Get 20M+ Full-Text Papers For Less Than $1.50/day. Start a 14-Day Trial for You or Your Team.

Learn More →

Influence of Preservation of Normal Knee Contact Stress on Other Compartments with respect to the Tibial Insert Design for Unicompartmental Knee Arthroplasty

Influence of Preservation of Normal Knee Contact Stress on Other Compartments with respect to the... Hindawi Applied Bionics and Biomechanics Volume 2019, Article ID 9246379, 9 pages https://doi.org/10.1155/2019/9246379 Research Article Influence of Preservation of Normal Knee Contact Stress on Other Compartments with respect to the Tibial Insert Design for Unicompartmental Knee Arthroplasty 1 2 2 Yong-Gon Koh , Kyoung-Mi Park , and Kyoung-Tak Kang Joint Reconstruction Center, Department of Orthopaedic Surgery, Yonsei Sarang Hospital, 10 Hyoryeong-ro, Seocho-gu, Seoul 06698, Republic of Korea Department of Mechanical Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea Correspondence should be addressed to Kyoung-Tak Kang; tagi1024@gmail.com Received 28 January 2019; Revised 2 August 2019; Accepted 11 October 2019; Published 14 November 2019 Academic Editor: Fong-Chin Su Copyright © 2019 Yong-Gon Koh et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Recent advances in imaging technology and additive manufacturing have led to the introduction of customized unicompartmental knee arthroplasty (UKA) that can potentially improve functional performance due to customized geometries, including customized sagittal and coronal curvature and enhanced bone preservation. The purpose of this study involved evaluating the biomechanical effect of the tibial insert design on the customized medial UKA using computer simulations. We developed sagittal and coronal curvatures in a native knee mimetic femoral component design. We utilized three types of tibial insert design: flat, anatomy mimetic, and conforming design. We evaluated contact stress on the tibial insert and other compartments, including the lateral meniscus and articular cartilage, under gait and squat loading conditions. For the conforming UKA design, the tibial insert and lateral meniscus exhibited the lowest contact stress under stance phase gait cycle. However, for the conforming UKA design, the tibial insert and lateral meniscus exhibited the highest contact stress under swing phase gait cycle. For the flat UKA design, the articular cartilage exhibited the lowest contact stress under gait and squat loading conditions. The anatomy mimetic UKA design exhibited the most normal-like contact stress on the other compartments under gait and squat loading conditions. The results reveal the importance of conformity between the femoral component and the tibial insert in the customized UKA. Based on the results on the femoral component as well as the tibial insert in the customized UKA, the anatomy mimetic design preserves normal knee joint biomechanics and thus may prevent progressive osteoarthritis of the other knee compartments. outcomes, and lower complication rates [5]. However, UKA 1. Introduction involves a demanding surgical technique, and precise com- Osteoarthritis (OA) typically first affects the medial compart- ponent positioning is essential [6]. ment of the tibiofemoral (TF) joint [1] and is a growing Although patient factors play a role in UKA survivorship, concern in younger patients [2]. There are various surgical current UKA designs present an important limitation [7]. treatments for isolated medial compartment arthritis, includ- Various anatomical studies indicate a wide range of variabil- ing unicompartmental knee arthroplasty (UKA), total knee ity in the size and shape of the medial and lateral tibial arthroplasty (TKA), and high tibial osteotomy [3]. The components [8, 9]. High early failure rates are reported in utilization rate of UKA exhibits a growth rate three times obese patients for designs with an inset or narrow tibia, while than that of TKA. Outstanding and dependable clinical early results for wider tibial components exhibit lower early failure rates [10, 11]. Asians exhibit a smaller build and results in the first decade of its use led surgeons to expand the indication for UKA to younger and more active patients stature when compared to their Western counterparts. How- [4]. The advantages include a faster recovery rate due to ever, most prostheses currently available in the market are minimally invasive surgery, less bone loss, better functional produced to fit the physique of Caucasian patients [12]. 2 Applied Bionics and Biomechanics (a) (b) Figure 1: (a) Intersection curves were used to extract the articulating surface geometry in the sagittal and coronal planes and (b) in the development of the femoral component of the patient-specific UKA using sagittal curves and constant coronal curves. The aforementioned difference was also observed in terms of FC UKA AMC UKA CC UKA sex, in addition to ethnicity [13, 14]. To solve the problem, patient-specific or customized implants are developed and introduced [15]. A customized UKA can provide superior cortical bone coverage and fit with minimal overhang and undercoverage compared to off-the-shelf UKA [16]. Addi- tionally, a recent computer simulation study indicates that a customized UKA can yield mechanics closer to that of a healthy knee joint [17]. A potential disadvantage of a completely customized UKA is variability in the coronal and sagittal curvature of Figure 2: Cross-sections of the femoral component and tibial insert the femoral component, which results in point loading at of the customized UKA used in this study, with three different select flexion angles when a curved tibial insert is used [18]. conformities. To address this problem, a flat polyethylene (PE) tibial insert is paired with a constant coronal curvature femoral compo- nent, and this guarantees constant loading conditions over (version 7.0; Siemens PLM Software, Torrance, CA, USA) a large area, irrespective of the flexion angle [15, 17, 18]. and fitted with rational B splines (Figure 1(a)) [17, 18, 21–23]. However, this type of flat design involves a problem that does The patient’s bone defines the sagittal geometry of not describe tibial insert anatomy. the femoral component. Thus, the sagittal geometry is The aim of this study involved evaluating the biomechan- completely patient-specific, and the resultant sagittal implant ics of different tibial insert conformity designs to provide a radii vary along the anteroposterior dimension of the implant design that is closer to that of a healthy knee joint. Thus, [17, 18, 21–23]. The coronal curvatures of the patient are we developed three different tibial insert surface designs: flat, measured at multiple positions along the length of the anatomy mimetic, and conforming tibial insert customized femoral condyle. An average curvature is then derived for UKAs. We hypothesize that the anatomy mimetic custom- each patient. Using this approach, a patient-derived constant ized UKA provides biomechanics closer to that of the healthy coronal curvature is achieved (Figure 1(b)). The tibial com- knee joint. ponent is designed based on the CT and MRI data of the patient’s tibia to ensure complete cortical rim coverage. With this method, the patient receives an implant with an 2. Materials and Methods optimized fit. The tibial plateau and inserts are designed for minimal bone cut and provide a smooth articulating surface 2.1. Design of Customized UKA. The customized medial UKA for the femoral component. The tibial component is patient- was designed by using a preexisting three-dimensional (3D) specific, and thus, it can potentially provide complete cortical knee joint model [17, 19–21]. The customized medial UKA rim coverage, which cannot be achieved with a conventional design was initiated with the acquisition of medical image implant [24]. data. Planes were introduced using the intersection of We designed three different tibial insert conformities condyles in both sagittal and coronal views. Intersection (Figure 2). Generally, the flat design is used for the tibial curves were used to extract the articulating surface geometry insert in a fixed-bearing UKA [25], which is similar to a in both planes, which were imported into Unigraphics NX customized fixed-bearing UKA. Additionally, the customized Applied Bionics and Biomechanics 3 Table 1: Material properties of the FE model. Young’s modulus (MPa) Poisson’s ratio CoCrMo alloy 220,000 0.30 UHMWPE 685 0.47 Ti6Al4V alloy 110,000 0.30 PMMA 1,940 0.40 resonance imaging sets of the subject. The description is available in previous studies [27, 28]. The ligaments were simulated as nonlinear force elements, and their parabolic and linear equations are as follows: if ε <0, f ðεÞ =0;if 0 ≤ ε ≤ 2ε , f ðεÞ = kε /4ε ; and if ε >2ε , f ðεÞ = kðε − ε Þ, 1 1 1 1 where f denotes the tension of the ligament, ε denotes the ligament strain, and k is the stiffness coefficient of each ligament. The linear range threshold was specified as ε =0:03. In all test scenarios applied in this study, the soft tissue elements remained in the same position. The bony structures were modeled as rigid bodies using four-node shell elements [29] while the interfaces between the articular cartilage and the bones were modeled as fully bonded [29]. Six pairs of tibiofemoral contact between the femoral carti- Figure 3: Validated FE native knee model used in this study, including TF and PF joints and major ligaments. lage and the meniscus, the meniscus and the tibial cartilage, and the femoral cartilage and the tibial cartilage were mod- eled for both the medial and lateral sides of the joint [17]. design exhibits variability in the coronal curvature of the femoral component and results in point loading at select The heights of the tibial insert for the three different designs flexion angles when a curved tibial insert is used [17, 18]. were matched to the original bone anatomy using a neutral To address that problem, a flat tibial insert is paired with a mechanical alignment, cutting the tibia orthogonal to the constant coronal curvature femoral component, and this coronal tibial mechanical axis [17]. The rotating axis was provides constant loading conditions over a large area, irre- defined as the line parallel to the lateral edge of the tibial spective of the flexion angle [17, 18]. Therefore, we developed baseplate passing the center of the femoral component fixa- tibial insert conformity in flat customized (FC) UKA as the tion peg. For the implanted model, a 1 mm cement gap was initial design. For the second design, the real medial geom- simulated between the component and the bone. The mate- etry was measured, and a medial anatomy mimetic custom- rials of the femoral component, PE insert, tibial baseplate, ized (AMC) UKA was developed. The sagittal cross-section and bone cement included cobalt-chromium-molybdenum of the medial tibial insert has a concave geometry similar to (CoCrMo) alloy, ultrahigh-molecular-weight polyethylene that of the native medial tibial cartilage, including a shallow (UHMWPE), titanium alloy (Ti6Al4V), and polymethyl curvature for overcoming the stability provided by the methacrylate (PMMA), respectively (Table 1) [17, 20, 30]. missing meniscus. As previously mentioned, the femoral The femoral component requires contact with the tibial component coronal curvature varies, and edge loading insert, and the coefficient of friction between the PE and may occur in the conforming design. However, the implant the femoral component was selected as 0.04 [30]. is used in the customized UKA, and various tibial insert The FE simulation comprised three types of loading con- designs can be applied. Therefore, the third design corre- ditions corresponding to the loads used in the experiment for sponds to a conforming customized (CC) UKA. Addition- model validation and the prediction of daily activity loading ally, the femoral component designs were identical in the scenarios. For the first loading condition, 150 N was applied ° ° customized UKA. to the tibia at 30 and 90 flexion in the FE knee joint to mea- sure anterior-posterior (AP) tibial translations [19]. Further- 2.2. Finite Element Model. The 3D medical imaging data used more, a second axial loading of 1,150 N was applied to the for the customized UKA design were also used in the devel- model to obtain contact stresses, which were compared to opment of the finite element (FE) model [17, 19, 20]. The those reported in a published study on the FE knee joint intact knee joint model had previously been developed and model [29]. The third loading condition, which corresponds validated [17, 19, 20], and the procedure can be found in to the gait cycle, and squat loading conditions, was applied to the literature. The FE model comprises the TF and patellofe- evaluate knee joint mechanics. Computational analysis was moral (PF) joints and major ligaments (Figure 3). conducted by applying an AP force to the femur with respect All ligament bundles were modeled as nonlinear to the compressive load applied to the hip, with constrained springs, and the material properties were obtained from femoral internal-external rotation, free medial-lateral trans- a previous study [26]. The ligament insertion points were lation, and knee flexion determined through a combination set with respect to the anatomy obtained from magnetic of the vertical hip and the load of the quadriceps. Thus, a 4 Applied Bionics and Biomechanics 16 16 14 14 12 12 10 10 8 8 6 6 4 4 2 2 0 0 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 Gait cycle (%) Squat loading (%) FC UKA FC UKA AMC UKA AMC UKA CC UKA CC UKA (a) (b) Figure 4: Comparison of the contact stress on the PE insert of three customized UKA designs with three different conformities under (a) gait and (b) squat loading conditions. six-degree-of-freedom TF joint was created [31–33]. A the different studies, such as the thickness of the cartilage proportional-integral-derivative controller was incorporated and meniscus. The significant consistency between the vali- into the computational model to control the quadriceps in dation results and the results reported in extant studies is a manner similar to that in a previous experiment [34]. A indicative of the validity of the results obtained with the FE control system was used to calculate the instantaneous model in this study. displacement of the quadriceps muscle, and this was required to match the same target flexion profile used in 3.2. Comparison of the Contact Stress on the PE Insert and the experiment. Internal-external and varus-valgus torques Other Compartments of the Customized UKA Designs with were applied to the tibia while the remaining tibial Three Different Conformities against That on a Native Knee degrees-of-freedom were constrained [31–33]. under Gait Cycle and Squat Loading Conditions. Figure 4 The FE model was analyzed using ABAQUS software shows the contact stress on the PE insert of the three different (version 6.11; Simulia, Providence, RI, USA). The study tibial insert designs for the customized UKA under gait and investigated and compared the contact stress on the PE insert squat loading conditions. During the stance phase gait cycle, and other compartments of the customized UKA designs adifference was observed in the PE insert contact stress of the with three different conformities to a native knee. The three different tibial insert designs for the customized UKA. kinematics were calculated based on Grood and Suntay’s The same trend was also observed under the squat loading definition of a joint coordinate system [35]. conditions. CC UKA exhibited the lowest PE inset contact stress under stance phase gait cycle, followed by AMC UKA and FC UKA. Under the squat loading conditions, CC 3. Results UKA exhibited the lowest PE insert contact stress. During the swing phase, CC UKA exhibited the highest PE inset 3.1. Intact Model Validation. The intact FE model was compared to the experiment using the Fe model’s subject contact stress, followed by AMC UKA and FC UKA. for validation purposes. Under the loading condition with a Figure 5 shows the contact stress on the lateral meniscus 30 flexion, the anterior tibial translation was 2.83 mm in for different tibial insert designs and a native knee joint under the experiment and 2.54 mm in the FE model, and the poste- gait and squat loading conditions. Contact stress on the lat- eral meniscus in the native knee was higher than that in the rior tibial translation was 2.12 mm in the experiment and 2.18 mm in the FE model. At 90 flexion, the anterior tibial three different tibial insert designs for the customized UKA translation was 3.32 mm in the experiment and 3.09 mm in during the stance phase gait cycle. The trend of contact stress the FE model, and the posterior tibial translation was on the lateral meniscus was also observed under deep flexion 2.64 mm in the experiment and 2.71 mm in the FE model. squat loading conditions. The lateral meniscus, like the PE The experimental results show good agreement with those insert, exhibited high contact stress during the stance phase obtained using the FE model [19]. Furthermore, the intact and low contact stress during the swing phase for the three FE model was validated by comparing it with computational different tibial insert designs for the customized UKA, com- pared to the native knee. results from previous studies. Under an axial load of 1,150 N, average contact stresses of 3.1 MPa and 1.53 MPa were Figure 6 shows the contact stress on the articular cartilage for the three different tibial insert designs for the customized observed on the medial and lateral menisci, respectively. Both are within 6% of the 2.9 MPa and 1.45 MPa contact UKA under gait and squat loading conditions. During the stress values reported by Pena et al. [29]. These minor gait cycle, contact stress on the articular cartilage in the native knee was lower than that in the three different tibial differences may be due to geometrical variations between Contract stress on PE insert (MPa) Contract stress on PE insert (MPa) Applied Bionics and Biomechanics 5 10 10 9 9 8 8 7 7 6 6 5 5 4 4 3 3 2 2 1 1 0 0 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 Gait cycle (%) Squat loading (%) FC UKA CC UKA FC UKA CC UKA AMC UKA Native knee AMC UKA Native knee (a) (b) Figure 5: Comparison of the contact stress on the lateral meniscus in three customized UKA designs with three different conformities against that on a native knee under (a) gait and (b) squat loading conditions. 4.5 4.5 4 4 3.5 3.5 3 3 2.5 2.5 2 2 1.5 1.5 1 1 0.5 0.5 0 0 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 Gait cycle (%) Squat loading (%) FC UKA CC UKA FC UKA CC UKA AMC UKA Native knee AMC UKA Native knee (a) (b) Figure 6: Comparison of the contact stress on the articular cartilage in three customized UKA designs with three different conformities against that on a native knee under (a) gait and (b) squat loading conditions. follow-up duration of ten years, medial UKA is associated insert designs for the customized UKA. FC UKA and CC UKA exhibited higher contact stress on the articular cartilage with excellent clinical and radiographic results [38]. than on the native knee in the swing phase. Furthermore, the Although the ten-year survival rate is excellent, radiographic CC UKA exhibited higher contact stress on the articular car- signs of progression of OA were observed in the other com- tilage than on the native knee under high flexion squat load- partments [38]. Theoretically, UKA requires a technically demanding procedure and precise component positioning ing conditions. Under gait and squat loading conditions, the contact stress on the lateral meniscus and articular cartilage [6, 39]. Furthermore, UKA entails challenges due to surgical indicates that the AMC UKA is closest to normal contact difficulties, such as device failures, residual pain, subsidence, mechanics. and OA progression in the other compartments [38, 40]. To overcome this problem, a customized instrumentation tech- nique is applied to UKA. 4. Discussion Bell et al. evaluated the accuracy and clinical outcomes of The most important finding of this study is that the AMC the customized instrumentation implementation technique UKA exhibits close to native knee contact mechanics. There- using a fixed-bearing UKA [41]. They proved that the tech- fore, the AMC UKA prevents progressive OA of other nique might offer specific advantages to surgeons who per- form lower volumes of UKA and can potentially improve compartments. We evaluated contact stress, which is closely related both clinical outcomes and implant survivorship of UKA to degenerative OA of the knee joint after medial UKA and achieve greater consistency in results [41]. However, it [36, 37]. A previous study indicates that after a minimum is not possible for this type of customized instrumentation Contract stress on lateral meniscus (MPa) Contract stress on lateral meniscus (MPa) Contract stress on articular cartilage (MPa) Contract stress on lateral meniscus (MPa) 6 Applied Bionics and Biomechanics On the lateral side, the cartilage layer of the TF exhibits to resolve the effect of morphology with respect to ethnicity and gender differences. The Asian population exhibits a an elastic modulus of 15 MPa. In contrast to the cartilage smaller build and stature compared to the Western popula- layers, the tibial articular insert exhibits an elastic modulus of 685 MPa. Consequently, the material characteristics of tion [12]. A majority of conventional UKA prostheses are designed to match the Caucasian physique [42]. In UKA, the medial and lateral compartments differ by more than 40 the geometry of the femoral and tibial components should times. Notably, other compartments in the AMC UKA have match the resected surface to the maximum extent possible the advantage of contact mechanics similar to that of the to provide optimal stability and load transfer [42]. Koeck native knee in swing phase gait and high flexion. CC UKA and FC UKA showed kinematic change, which led to lateral et al. indicated that customized instrumentation and implant using fixed-bearing UKA can reliably restore the leg axis, cartilage contact stress because they did not restore tibial obtain a medial proximal tibial angle of 90 insert conformity and native anatomy. This trend was found , prevent implant malpositioning, and ensure maximal tibial coverage [43]. for swing phase gait and high flexion squat loading condi- Steklov et al. indicated that a constant coronal curvature tions. The most important advantage of the AMC UKA was observed under high flexion where the effect of the anatomy can be applied to a customized UKA by measuring coronal curvatures across the femoral condyle in each patient and mimetic tibial insert was visible as the J curve of the femur by deriving the average curvature [18]. This novel approach was maintained in the femoral component. combines the unique benefits of customized geometry with The contact area is most important during the stance proven design concepts in UKA to minimize PE wear [18]. phase gait cycle and deep flexion during squat loading condi- tions, during which the axial force was primarily visible. However, as previously mentioned, the customized UKA should overcome edge loading at select flexion angles when However, the contact area, as well as the kinematics, is also a curved tibial insert is used [17]. To address the problem, a crucial during the swing phase gait cycle and high flexion flat PE tibial insert is paired with the constant coronal curva- under squat loading conditions. Unfortunately, both the ture femoral component, and this ensures constant loading femur and tibial mimetic AMC UKAs could not preserve perfect normal knee contact mechanism. An important fac- conditions over a large area, irrespective of the flexion angle [17, 18]. However, in a native knee, the medial and lateral tib- tor is that change in the mechanism due to change in material ial plateaus exhibit anatomical asymmetric geometries with a stiffness plays the most crucial role, even if it corresponds to slightly dished medial plateau and a convex lateral plateau. an anatomy mimetic design. Furthermore, the tibial insert The result presents the pattern of various contact stresses could not perfectly replicate the role of mobile meniscus characteristics. Generally, there are significant differences on the PE tibial insert and other compartments in the cus- tomized UKA with respect to different tibial insert designs. between the biomechanics of the medial and lateral menisci An interesting finding was observed in CC UKA: the CC [45, 46]. The medial meniscus is significantly less mobile than the lateral meniscus due to its attachment to the medial UKA exhibited increased contact stress on the PE insert dur- ing the swing phase gait cycle and high flexion during squat collateral ligament and larger insertion areas. In terms of clinical relevance, it is not possible to apply a loading conditions. The most influential factor on contact stress is the contact area. Therefore, the CC UKA with an conforming design to the tibial insert when a customized increased contact area should exhibit decreased contact UKA is developed. Bernasek et al. reported unsatisfactory stress, although it did not exhibit this. Generally, conforming results regarding the insertion of the same type of conform- design is used in the mobile-bearing UKA [36]. However, in ing fixed-bearing UKA [47]. Furthermore, a previous study this study, the conforming design was used in the fixed- indicated that significant degenerative changes in the other bearing UKA. Abnormal kinematics and increased contact compartments occurred in only one of the eighty-seven stress were observed, and this was similar for the swing phase knees in which an unconstrained UKA was implanted [48]. and high flexion. When flexion increased, for the CC UKA, The results support the reliability of this study. The AMC movement of the tibial insert restores a similar contact area. UKA should apply mobile characteristics to the tibial insert However, edge loading may occur in a fixed condition. For to preserve knee mechanics closer to that of the native knee. the stance phase gait and deep flexion under squat loading However, a reason for the application of the conforming conditions in which the flexion angle does not show a signif- design to mobile-bearing UKA involves preventing bearing icant effect, the CC UKA exhibited the lowest contact stress dislocation. Therefore, a spinout mechanism should be con- due to the advantage of conformity. sidered for preventing dislocation through the application In the lateral meniscus, a trend of contact stress simi- of mobile characteristics in the AMC UKA to preserve native lar to that in the PE insert was observed in the customized knee mechanics. UKA for the three different tibial insert designs. This Two strengths of this study are as follows: First, unlike trend is probably due to the role the menisci play in pro- previous UKA studies, the FE model included the tibia, tecting the TF cartilage layers when the load is transferred. femur, and related soft tissues [49, 50]. Second, unlike the When the UKA was implanted, the contact stress on the current biomechanical UKA model, this study included the lateral meniscus is lower than that in the native knee dur- application of gait and squat loading conditions [49, 50]. ing the stance phase of the gait cycle in which loading is Nevertheless, several limitations should also be noted. mainly involved. This is primarily due to the change in First, the bony structures were assumed as rigid, while in real- stiffness between the medial and lateral compartments ity, bone exhibits cortical and cancellous tissues. However, induced in the knee by the device [44]. the primary purpose of the study did not involve evaluating Applied Bionics and Biomechanics 7 the effects of different prostheses on bone. Furthermore, the States,” The Journal of Arthroplasty, vol. 23, no. 3, pp. 408– 412, 2008. assumption exerted minimal influence on the study because the stiffness of bone exceeds that of the relevant soft tissues [3] J.-P. Whittaker, D. D. R. Naudie, J. P. McAuley, R. W. McCalden, S. J. MacDonald, and R. B. Bourne, “Does bear- [29]. Second, the computational model represented a cus- ing design influence midterm survivorship of unicompart- tomized UKA and the results are not necessarily expected mental arthroplasty?,” Clinical Orthopaedics and Related to extend to other implant designs, such as the customized Research, vol. 468, no. 1, pp. 73–81, 2010. mobile-bearing UKA. Third, the material properties and [4] K. G. Vince and L. T. Cyran, “Unicompartmental knee attachment points of the ligaments were assumed in the arthroplasty: new indications, more complications?,” The Jour- model based on values from extant studies, although signifi- nal of Arthroplasty, vol. 19, 4 Suppl 1, pp. 9–16, 2004. cant variability exists regarding reported values. However, [5] G. C. R. Keene and M. C. Forster, “(iii) Modern unicompart- the objective did not involve determining the actual values mental knee replacement,” Current Orthopaedics, vol. 19, of ligament forces but determining the effect of variability no. 6, pp. 428–445, 2005. in a customized fixed-bearing UKA with respect to the tibial [6] F. Zambianchi, V. Digennaro, A. Giorgini et al., “Surgeon’s insert design corresponding to the femoral component. Fur- experience influences UKA survivorship: a comparative study thermore, the advantage of computer simulation of a single between all-poly and metal back designs,” Knee surgery, sports subject is that we could determine the effects of the tibial traumatology, arthroscopy : official journal of the ESSKA, insert design of a customized UKA within the same individ- vol. 23, no. 7, pp. 2074–2080, 2015. ual and eliminate the effects of other variables, such as [7] W. Fitz, “Unicompartmental knee arthroplasty with use of weight, height, bony geometry, ligament properties, and novel patient-specific resurfacing implants and personalized component size [51]. jigs,” The Journal of bone and joint surgery American volume, vol. 91, Supplement 1, pp. 69–76, 2009. 5. Conclusion [8] J. Hashemi, N. Chandrashekar, B. Gill et al., “The geometry of the tibial plateau and its influence on the biomechanics of the The anatomy mimetic design, which retains the native tibial tibiofemoral joint,” The Journal of bone and joint surgery insert, exhibited significant contact mechanics improvement American volume, vol. 90, no. 12, pp. 2724–2734, 2008. over the customized UKA during gait and squat loading [9] E. Servien, M. Saffarini, S. Lustig, S. Chomel, and P. Neyret, conditions. The nonanatomic tibial insert geometry of the “Lateral versus medial tibial plateau: morphometric analysis customized UKA contributed to contact mechanics abnor- and adaptability with current tibial component design,” Knee malities, including the PE tibial insert and the other compart- surgery, sports traumatology, arthroscopy : official journal of ments. Therefore, the AMC UKA may represent an essential the ESSKA, vol. 16, no. 12, pp. 1141–1145, 2008. step in our attempt to restore the function of the native [10] K. R. Berend, A. V. Lombardi Jr., T. H. Mallory, J. B. Adams, mechanics of the knee. Based on the results for the femoral and K. L. Groseth, “Early failure of minimally invasive uni- component as well as the tibial insert in a customized UKA, compartmental knee arthroplasty is associated with obesity,” Clinical Orthopaedics and Related Research, vol. 440, no. &NA;, the anatomy mimetic design preserves normal knee biome- pp. 60–66, 2005. chanics and thus may prevent progressive osteoarthritis of [11] K. R. Berend, A. V. Lombardi Jr., and J. B. Adams, “Obesity, the other compartments. young age, patellofemoral disease, and anterior knee pain: identifying the unicondylar arthroplasty patient in the United Data Availability States,” Orthopedics, vol. 30, no. 5, pp. 19–23, 2007. [12] S. V. Vaidya, C. S. Ranawat, A. Aroojis, and N. S. Laud, The data used to support the findings of this study are “Anthropometric measurements to design total knee prosthe- included within the article. ses for the Indian population,” The Journal of Arthroplasty, vol. 15, no. 1, pp. 79–85, 2000. Conflicts of Interest [13] K. T. Kang, J. Son, O. R. Kwon et al., “Morphometry of femoral rotation for total knee prosthesis according to gen- The authors declare that there is no conflict of interests der in a Korean population using three-dimensional mag- regarding the publication of this paper. netic resonance imaging,” The Knee, vol. 23, no. 6, pp. 975–980, 2016. Authors’ Contributions [14] K. T. Kang, J. Son, O. R. Kwon et al., “Effects of measurement methods for tibial rotation axis on the morphometry in Yong-Gon Koh and Kyoung-Mi Park contributed equally to Korean populations by gender,” The Knee, vol. 24, no. 1, this work and should be considered co-first authors. pp. 23–30, 2017. [15] ConforMIS, Inc, Novemver 2019, https://www.conformis.com. References [16] D. P. Carpenter, R. R. Holmberg, M. J. Quartulli, and C. L. Barnes, “Tibial plateau coverage in UKA: a comparison of [1] A. Carr, G. Keyes, R. Miller, J. O'Connor, and J. Goodfellow, “Medial unicompartmental arthroplasty. A survival study of patient specific and off-the- shelf implants,” The Journal of Arthroplasty, vol. 29, no. 9, pp. 1694–1698, 2014. the Oxford meniscal knee,” Clinical Orthopaedics and Related Research, vol. 295, pp. 205–213, 1993. [17] K. T. Kang, J. Son, D. S. Suh, S. K. Kwon, O. R. Kwon, and Y. G. [2] D. L. Riddle, W. A. Jiranek, and F. J. McGlynn, “Yearly inci- Koh, “Patient-specific medial unicompartmental knee arthro- dence of unicompartmental knee arthroplasty in the United plasty has a greater protective effect on articular cartilage in 8 Applied Bionics and Biomechanics arthroplasty using computational simulation,” Bone & joint the lateral compartment: a finite element analysis,” Bone & joint research, vol. 7, no. 1, pp. 20–27, 2018. research, vol. 5, no. 11, pp. 552–559, 2016. [32] I. Kutzner, B. Heinlein, F. Graichen et al., “Loading of the knee [18] N. Steklov, J. Slamin, S. Srivastav, and D. D’Lima, “Unicom- partmental knee resurfacing: enlarged tibio-femoral contact joint during activities of daily living measured _in vivo_ in five subjects,” Journal of Biomechanics, vol. 43, no. 11, pp. 2164– area and reduced contact stress using novel patient-derived geometries,” Open Biomedical Engineering Journal, vol. 4, 2173, 2010. pp. 85–92, 2010. [33] J. P. Halloran, C. W. Clary, L. P. Maletsky, M. Taylor, A. J. Petrella, and P. J. Rullkoetter, “Verification of predicted [19] K. T. Kang, S. H. Kim, J. Son, Y. H. Lee, and Y. G. Koh, “Val- knee replacement kinematics during simulated gait in the idation of a computational knee joint model using an align- Kansas knee simulator,” Journal of biomechanical engineering, ment method for the knee laxity test and computed vol. 132, no. 8, p. 081010, 2010. tomography,” Bio-medical Materials and Engineering, vol. 28, no. 4, pp. 417–429, 2017. [34] K. T. Kang, Y. G. Koh, J. Son et al., “Finite element analysis of the biomechanical effects of 3 posterolateral corner [20] K. T. Kang, S. K. Kwon, J. Son, O. R. Kwon, J. S. Lee, and Y. G. reconstruction techniques for the knee joint,” Arthroscopy : Koh, “The increase in posterior tibial slope provides a positive the journal of arthroscopic & related surgery : official publica- biomechanical effect in posterior-stabilized total knee arthro- tion of the Arthroscopy Association of North America and the plasty,” Knee Surgery, Sports Traumatology, Arthroscopy, International Arthroscopy Association, vol. 33, no. 8, vol. 26, no. 10, pp. 3188–3195, 2018. pp. 1537–1550, 2017. [21] Y. G. Koh, K. M. Park, H. Y. Lee, and K. T. Kang, “Influ- [35] E. S. Grood and W. J. Suntay, “A joint coordinate system for ence of tibiofemoral congruency design on the wear of the clinical description of three-dimensional motions: applica- patient-specific unicompartmental knee arthroplasty using tion to the knee,” Journal of Biomechanical Engineering, finite element analysis,” Bone & joint research, vol. 8, no. 3, vol. 105, no. 2, pp. 136–144, 1983. pp. 156–164, 2019. [36] O. R. Kwon, K. T. Kang, J. Son et al., “Biomechanical compar- [22] D. J. Van Den Heever, C. Scheffer, P. J. Erasmus, and E. M. ison of fixed‐ and mobile‐bearing for unicomparmental knee Dillon, “Contact stresses in a patient-specific unicompart- arthroplasty using finite element analysis,” Journal of Ortho- mental knee replacement,” in Proceedings of the 2010 paedic Research : Official Publication of the Orthopaedic Annual International Conference of the IEEE Engineering Research Society, vol. 32, no. 2, pp. 338–345, 2014. in Medicine and Biology Society (EMBC 2010), pp. 5113– [37] N. A. Segal, D. D. Anderson, K. S. Iyer et al., “Baseline articular 5116, Buenos Aires, Argentina, 2010. contact stress levels predict incident symptomatic knee osteo- [23] W. B. Kurtz, J. E. Slamin, and S. W. Doody, “Bone preservation arthritis development in the MOST cohort,” Journal of Ortho- in a novel patient specific total knee replacement,” Reconstruc- paedic Research : Official Publication of the Orthopaedic tive Review, vol. 6, no. 1, pp. 23–29, 2016. Research Society, vol. 27, no. 12, pp. 1562–1568, 2009. [24] C. Fitzpatrick, D. FitzPatrick, J. Lee, and D. Auger, “Statistical [38] R. A. Berger, R. Michael Meneghini, J. J. Jacobs et al., “Results design of unicompartmental tibial implants and comparison of unicompartmental knee arthroplasty at a minimum of ten with current devices,” The Knee, vol. 14, no. 2, pp. 138–144, years of follow-up,” The Journal of bone and joint surgery American volume, vol. 87, no. 5, pp. 999–1006, 2005. [25] M. K. Harman, S. Schmitt, S. Rössing et al., “Polyethylene [39] M. H. Liow, T. Y. Tsai, D. Dimitriou, G. Li, and Y. M. Kwon, damage and deformation on fixed-bearing, non-conforming “Does 3-dimensional in vivo component rotation affect clini- unicondylar knee replacements corresponding to progressive cal outcomes in Unicompartmental knee arthroplasty?,” The changes in alignment and fixation,” Clinical Biomechanics Journal of Arthroplasty, vol. 31, no. 10, pp. 2167–2172, 2016. (Bristol, Avon), vol. 25, no. 6, pp. 570–575, 2010. [40] A. Lindstrand, A. Stenstrom, and S. Lewold, “Multicenter [26] L. Blankevoort and R. Huiskes, “Validation of a three- study of unicompartmental knee revision. PCA, Marmor, dimensional model of the knee,” Journal of Biomechanics, and St Georg compared in 3,777 cases of arthrosis,” Acta vol. 29, no. 7, article 0021929095001492, pp. 955–961, 1996. Orthopaedica Scandinavica, vol. 63, no. 3, pp. 256–259, 1992. [27] K. F. Bowman Jr. and J. K. Sekiya, “Anatomy and biomechan- [41] S. W. Bell, J. Stoddard, C. Bennett, and N. J. London, “Accu- ics of the posterior cruciate ligament, medial and lateral sides racy and early outcomes in medial unicompartmental knee of the knee,” Sports Medicine and Arthroscopy Review, arthroplasty performed using patient specific instrumenta- vol. 18, no. 4, pp. 222–229, 2010. tion,” The Knee, vol. 21, Supplemenrt 1, pp. S33–S36, 2014. [28] J. L. Baldwin, “The anatomy of the medial patellofemoral liga- [42] S. Surendran, D. S. Kwak, U. Y. Lee et al., “Anthropometry of ment,” The American Journal of Sports Medicine, vol. 37, the medial tibial condyle to design the tibial component for no. 12, pp. 2355–2361, 2009. unicondylar knee arthroplasty for the Korean population,” [29] E. Peña, B. Calvo, M. A. Martinez, D. Palanca, and M. Doblaré, Knee surgery, sports traumatology, arthroscopy, vol. 15, no. 4, “Why lateral meniscectomy is more dangerous than medial pp. 436–442, 2007. meniscectomy. A finite element study,” Journal of Orthopaedic [43] F. X. Koeck, J. Beckmann, C. Luring, B. Rath, J. Grifka, and Research : Official Publication of the Orthopaedic Research E. Basad, “Evaluation of implant position and knee alignment Society, vol. 24, no. 5, pp. 1001–1010, 2006. after patient-specific unicompartmental knee arthroplasty,” [30] A. Godest, M. Beaugonin, E. Haug, M. Taylor, and P. J. Greg- The Knee, vol. 18, no. 5, pp. 294–299, 2011. son, “Simulation of a knee joint replacement during a gait cycle [44] K. T. Kang, O. R. Kwon, J. Son, D. S. Suh, S. K. Kwon, and Y. G. using explicit finite element analysis,” Journal of Biomechanics, Koh, “Effect of joint line preservation on mobile-type bearing vol. 35, no. 2, pp. 267–275, 2002. unicompartmental knee arthroplasty: finite element analysis,” [31] K. T. Kang, Y. G. Koh, J. Son et al., “Measuring the effect of Australasian Physical & Engineering Sciences in Medicine, femoral malrotation on knee joint biomechanics for total knee vol. 41, no. 1, pp. 201–208, 2018. Applied Bionics and Biomechanics 9 [45] A. J. Fox, A. Bedi, and S. A. Rodeo, “The basic science of human knee menisci: structure, composition, and function,” Sports health, vol. 4, no. 4, pp. 340–351, 2012. [46] I. D. McDermott, S. D. Masouros, and A. A. Amis, “Biome- chanics of the menisci of the knee,” Current Orthopaedics, vol. 22, no. 3, pp. 193–201, 2008. [47] T. L. Bernasek, J. A. Rand, and R. S. Bryan, “Unicompartmen- tal porous coated anatomic total knee arthroplasty,” Clinical Orthopaedics and Related Research, vol. 236, pp. 52–59, 1988. [48] W. A. Hodge and H. P. Chandler, “Unicompartmental knee replacement: a comparison of constrained and unconstrained designs,” The Journal of bone and joint surgery American vol- ume, vol. 74, no. 6, pp. 877–883, 1992. [49] S. Inoue, M. Akagi, S. Asada, S. Mori, H. Zaima, and M. Hashida, “The valgus inclination of the tibial component increases the risk of medial tibial condylar fractures in unicompartmental knee arthroplasty,” The Journal of Arthroplasty, vol. 31, no. 9, pp. 2025–2030, 2016. [50] E. C. Pegg, J. Walter, S. J. Mellon et al., “Evaluation of factors affecting tibial bone strain after unicompartmental knee replacement,” Journal of Orthopaedic Research : Official Publication of the Orthopaedic Research Society, vol. 31, no. 5, pp. 821–828, 2013. [51] K. T. Kang, Y. G. Koh, J. Son, O. R. Kwon, J. S. Lee, and S. K. Kwon, “Influence of increased posterior tibial slope in total knee arthroplasty on knee joint biomechanics: a computa- tional simulation study,” The Journal of Arthroplasty, vol. 33, no. 2, pp. 572–579, 2018. International Journal of Advances in Rotating Machinery Multimedia Journal of The Scientific Journal of Engineering World Journal Sensors Hindawi Hindawi Publishing Corporation Hindawi Hindawi Hindawi Hindawi www.hindawi.com Volume 2018 http://www www.hindawi.com .hindawi.com V Volume 2018 olume 2013 www.hindawi.com Volume 2018 www.hindawi.com Volume 2018 www.hindawi.com Volume 2018 Journal of Control Science and Engineering Advances in Civil Engineering Hindawi Hindawi www.hindawi.com Volume 2018 www.hindawi.com Volume 2018 Submit your manuscripts at www.hindawi.com Journal of Journal of Electrical and Computer Robotics Engineering Hindawi Hindawi www.hindawi.com Volume 2018 www.hindawi.com Volume 2018 VLSI Design Advances in OptoElectronics International Journal of Modelling & Aerospace International Journal of Simulation Navigation and in Engineering Engineering Observation Hindawi Hindawi Hindawi Hindawi Volume 2018 Volume 2018 Hindawi www.hindawi.com Volume 2018 www.hindawi.com Volume 2018 www.hindawi.com www.hindawi.com www.hindawi.com Volume 2018 International Journal of Active and Passive International Journal of Antennas and Advances in Chemical Engineering Propagation Electronic Components Shock and Vibration Acoustics and Vibration Hindawi Hindawi Hindawi Hindawi Hindawi www.hindawi.com Volume 2018 www.hindawi.com Volume 2018 www.hindawi.com Volume 2018 www.hindawi.com Volume 2018 www.hindawi.com Volume 2018 http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Applied Bionics and Biomechanics Hindawi Publishing Corporation

Influence of Preservation of Normal Knee Contact Stress on Other Compartments with respect to the Tibial Insert Design for Unicompartmental Knee Arthroplasty

Loading next page...
 
/lp/hindawi-publishing-corporation/influence-of-preservation-of-normal-knee-contact-stress-on-other-ZBQ1XSLA3P
Publisher
Hindawi Publishing Corporation
Copyright
Copyright © 2019 Yong-Gon Koh et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
ISSN
1176-2322
eISSN
1754-2103
DOI
10.1155/2019/9246379
Publisher site
See Article on Publisher Site

Abstract

Hindawi Applied Bionics and Biomechanics Volume 2019, Article ID 9246379, 9 pages https://doi.org/10.1155/2019/9246379 Research Article Influence of Preservation of Normal Knee Contact Stress on Other Compartments with respect to the Tibial Insert Design for Unicompartmental Knee Arthroplasty 1 2 2 Yong-Gon Koh , Kyoung-Mi Park , and Kyoung-Tak Kang Joint Reconstruction Center, Department of Orthopaedic Surgery, Yonsei Sarang Hospital, 10 Hyoryeong-ro, Seocho-gu, Seoul 06698, Republic of Korea Department of Mechanical Engineering, Yonsei University, 50 Yonsei-ro, Seodaemun-gu, Seoul 03722, Republic of Korea Correspondence should be addressed to Kyoung-Tak Kang; tagi1024@gmail.com Received 28 January 2019; Revised 2 August 2019; Accepted 11 October 2019; Published 14 November 2019 Academic Editor: Fong-Chin Su Copyright © 2019 Yong-Gon Koh et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. Recent advances in imaging technology and additive manufacturing have led to the introduction of customized unicompartmental knee arthroplasty (UKA) that can potentially improve functional performance due to customized geometries, including customized sagittal and coronal curvature and enhanced bone preservation. The purpose of this study involved evaluating the biomechanical effect of the tibial insert design on the customized medial UKA using computer simulations. We developed sagittal and coronal curvatures in a native knee mimetic femoral component design. We utilized three types of tibial insert design: flat, anatomy mimetic, and conforming design. We evaluated contact stress on the tibial insert and other compartments, including the lateral meniscus and articular cartilage, under gait and squat loading conditions. For the conforming UKA design, the tibial insert and lateral meniscus exhibited the lowest contact stress under stance phase gait cycle. However, for the conforming UKA design, the tibial insert and lateral meniscus exhibited the highest contact stress under swing phase gait cycle. For the flat UKA design, the articular cartilage exhibited the lowest contact stress under gait and squat loading conditions. The anatomy mimetic UKA design exhibited the most normal-like contact stress on the other compartments under gait and squat loading conditions. The results reveal the importance of conformity between the femoral component and the tibial insert in the customized UKA. Based on the results on the femoral component as well as the tibial insert in the customized UKA, the anatomy mimetic design preserves normal knee joint biomechanics and thus may prevent progressive osteoarthritis of the other knee compartments. outcomes, and lower complication rates [5]. However, UKA 1. Introduction involves a demanding surgical technique, and precise com- Osteoarthritis (OA) typically first affects the medial compart- ponent positioning is essential [6]. ment of the tibiofemoral (TF) joint [1] and is a growing Although patient factors play a role in UKA survivorship, concern in younger patients [2]. There are various surgical current UKA designs present an important limitation [7]. treatments for isolated medial compartment arthritis, includ- Various anatomical studies indicate a wide range of variabil- ing unicompartmental knee arthroplasty (UKA), total knee ity in the size and shape of the medial and lateral tibial arthroplasty (TKA), and high tibial osteotomy [3]. The components [8, 9]. High early failure rates are reported in utilization rate of UKA exhibits a growth rate three times obese patients for designs with an inset or narrow tibia, while than that of TKA. Outstanding and dependable clinical early results for wider tibial components exhibit lower early failure rates [10, 11]. Asians exhibit a smaller build and results in the first decade of its use led surgeons to expand the indication for UKA to younger and more active patients stature when compared to their Western counterparts. How- [4]. The advantages include a faster recovery rate due to ever, most prostheses currently available in the market are minimally invasive surgery, less bone loss, better functional produced to fit the physique of Caucasian patients [12]. 2 Applied Bionics and Biomechanics (a) (b) Figure 1: (a) Intersection curves were used to extract the articulating surface geometry in the sagittal and coronal planes and (b) in the development of the femoral component of the patient-specific UKA using sagittal curves and constant coronal curves. The aforementioned difference was also observed in terms of FC UKA AMC UKA CC UKA sex, in addition to ethnicity [13, 14]. To solve the problem, patient-specific or customized implants are developed and introduced [15]. A customized UKA can provide superior cortical bone coverage and fit with minimal overhang and undercoverage compared to off-the-shelf UKA [16]. Addi- tionally, a recent computer simulation study indicates that a customized UKA can yield mechanics closer to that of a healthy knee joint [17]. A potential disadvantage of a completely customized UKA is variability in the coronal and sagittal curvature of Figure 2: Cross-sections of the femoral component and tibial insert the femoral component, which results in point loading at of the customized UKA used in this study, with three different select flexion angles when a curved tibial insert is used [18]. conformities. To address this problem, a flat polyethylene (PE) tibial insert is paired with a constant coronal curvature femoral compo- nent, and this guarantees constant loading conditions over (version 7.0; Siemens PLM Software, Torrance, CA, USA) a large area, irrespective of the flexion angle [15, 17, 18]. and fitted with rational B splines (Figure 1(a)) [17, 18, 21–23]. However, this type of flat design involves a problem that does The patient’s bone defines the sagittal geometry of not describe tibial insert anatomy. the femoral component. Thus, the sagittal geometry is The aim of this study involved evaluating the biomechan- completely patient-specific, and the resultant sagittal implant ics of different tibial insert conformity designs to provide a radii vary along the anteroposterior dimension of the implant design that is closer to that of a healthy knee joint. Thus, [17, 18, 21–23]. The coronal curvatures of the patient are we developed three different tibial insert surface designs: flat, measured at multiple positions along the length of the anatomy mimetic, and conforming tibial insert customized femoral condyle. An average curvature is then derived for UKAs. We hypothesize that the anatomy mimetic custom- each patient. Using this approach, a patient-derived constant ized UKA provides biomechanics closer to that of the healthy coronal curvature is achieved (Figure 1(b)). The tibial com- knee joint. ponent is designed based on the CT and MRI data of the patient’s tibia to ensure complete cortical rim coverage. With this method, the patient receives an implant with an 2. Materials and Methods optimized fit. The tibial plateau and inserts are designed for minimal bone cut and provide a smooth articulating surface 2.1. Design of Customized UKA. The customized medial UKA for the femoral component. The tibial component is patient- was designed by using a preexisting three-dimensional (3D) specific, and thus, it can potentially provide complete cortical knee joint model [17, 19–21]. The customized medial UKA rim coverage, which cannot be achieved with a conventional design was initiated with the acquisition of medical image implant [24]. data. Planes were introduced using the intersection of We designed three different tibial insert conformities condyles in both sagittal and coronal views. Intersection (Figure 2). Generally, the flat design is used for the tibial curves were used to extract the articulating surface geometry insert in a fixed-bearing UKA [25], which is similar to a in both planes, which were imported into Unigraphics NX customized fixed-bearing UKA. Additionally, the customized Applied Bionics and Biomechanics 3 Table 1: Material properties of the FE model. Young’s modulus (MPa) Poisson’s ratio CoCrMo alloy 220,000 0.30 UHMWPE 685 0.47 Ti6Al4V alloy 110,000 0.30 PMMA 1,940 0.40 resonance imaging sets of the subject. The description is available in previous studies [27, 28]. The ligaments were simulated as nonlinear force elements, and their parabolic and linear equations are as follows: if ε <0, f ðεÞ =0;if 0 ≤ ε ≤ 2ε , f ðεÞ = kε /4ε ; and if ε >2ε , f ðεÞ = kðε − ε Þ, 1 1 1 1 where f denotes the tension of the ligament, ε denotes the ligament strain, and k is the stiffness coefficient of each ligament. The linear range threshold was specified as ε =0:03. In all test scenarios applied in this study, the soft tissue elements remained in the same position. The bony structures were modeled as rigid bodies using four-node shell elements [29] while the interfaces between the articular cartilage and the bones were modeled as fully bonded [29]. Six pairs of tibiofemoral contact between the femoral carti- Figure 3: Validated FE native knee model used in this study, including TF and PF joints and major ligaments. lage and the meniscus, the meniscus and the tibial cartilage, and the femoral cartilage and the tibial cartilage were mod- eled for both the medial and lateral sides of the joint [17]. design exhibits variability in the coronal curvature of the femoral component and results in point loading at select The heights of the tibial insert for the three different designs flexion angles when a curved tibial insert is used [17, 18]. were matched to the original bone anatomy using a neutral To address that problem, a flat tibial insert is paired with a mechanical alignment, cutting the tibia orthogonal to the constant coronal curvature femoral component, and this coronal tibial mechanical axis [17]. The rotating axis was provides constant loading conditions over a large area, irre- defined as the line parallel to the lateral edge of the tibial spective of the flexion angle [17, 18]. Therefore, we developed baseplate passing the center of the femoral component fixa- tibial insert conformity in flat customized (FC) UKA as the tion peg. For the implanted model, a 1 mm cement gap was initial design. For the second design, the real medial geom- simulated between the component and the bone. The mate- etry was measured, and a medial anatomy mimetic custom- rials of the femoral component, PE insert, tibial baseplate, ized (AMC) UKA was developed. The sagittal cross-section and bone cement included cobalt-chromium-molybdenum of the medial tibial insert has a concave geometry similar to (CoCrMo) alloy, ultrahigh-molecular-weight polyethylene that of the native medial tibial cartilage, including a shallow (UHMWPE), titanium alloy (Ti6Al4V), and polymethyl curvature for overcoming the stability provided by the methacrylate (PMMA), respectively (Table 1) [17, 20, 30]. missing meniscus. As previously mentioned, the femoral The femoral component requires contact with the tibial component coronal curvature varies, and edge loading insert, and the coefficient of friction between the PE and may occur in the conforming design. However, the implant the femoral component was selected as 0.04 [30]. is used in the customized UKA, and various tibial insert The FE simulation comprised three types of loading con- designs can be applied. Therefore, the third design corre- ditions corresponding to the loads used in the experiment for sponds to a conforming customized (CC) UKA. Addition- model validation and the prediction of daily activity loading ally, the femoral component designs were identical in the scenarios. For the first loading condition, 150 N was applied ° ° customized UKA. to the tibia at 30 and 90 flexion in the FE knee joint to mea- sure anterior-posterior (AP) tibial translations [19]. Further- 2.2. Finite Element Model. The 3D medical imaging data used more, a second axial loading of 1,150 N was applied to the for the customized UKA design were also used in the devel- model to obtain contact stresses, which were compared to opment of the finite element (FE) model [17, 19, 20]. The those reported in a published study on the FE knee joint intact knee joint model had previously been developed and model [29]. The third loading condition, which corresponds validated [17, 19, 20], and the procedure can be found in to the gait cycle, and squat loading conditions, was applied to the literature. The FE model comprises the TF and patellofe- evaluate knee joint mechanics. Computational analysis was moral (PF) joints and major ligaments (Figure 3). conducted by applying an AP force to the femur with respect All ligament bundles were modeled as nonlinear to the compressive load applied to the hip, with constrained springs, and the material properties were obtained from femoral internal-external rotation, free medial-lateral trans- a previous study [26]. The ligament insertion points were lation, and knee flexion determined through a combination set with respect to the anatomy obtained from magnetic of the vertical hip and the load of the quadriceps. Thus, a 4 Applied Bionics and Biomechanics 16 16 14 14 12 12 10 10 8 8 6 6 4 4 2 2 0 0 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 Gait cycle (%) Squat loading (%) FC UKA FC UKA AMC UKA AMC UKA CC UKA CC UKA (a) (b) Figure 4: Comparison of the contact stress on the PE insert of three customized UKA designs with three different conformities under (a) gait and (b) squat loading conditions. six-degree-of-freedom TF joint was created [31–33]. A the different studies, such as the thickness of the cartilage proportional-integral-derivative controller was incorporated and meniscus. The significant consistency between the vali- into the computational model to control the quadriceps in dation results and the results reported in extant studies is a manner similar to that in a previous experiment [34]. A indicative of the validity of the results obtained with the FE control system was used to calculate the instantaneous model in this study. displacement of the quadriceps muscle, and this was required to match the same target flexion profile used in 3.2. Comparison of the Contact Stress on the PE Insert and the experiment. Internal-external and varus-valgus torques Other Compartments of the Customized UKA Designs with were applied to the tibia while the remaining tibial Three Different Conformities against That on a Native Knee degrees-of-freedom were constrained [31–33]. under Gait Cycle and Squat Loading Conditions. Figure 4 The FE model was analyzed using ABAQUS software shows the contact stress on the PE insert of the three different (version 6.11; Simulia, Providence, RI, USA). The study tibial insert designs for the customized UKA under gait and investigated and compared the contact stress on the PE insert squat loading conditions. During the stance phase gait cycle, and other compartments of the customized UKA designs adifference was observed in the PE insert contact stress of the with three different conformities to a native knee. The three different tibial insert designs for the customized UKA. kinematics were calculated based on Grood and Suntay’s The same trend was also observed under the squat loading definition of a joint coordinate system [35]. conditions. CC UKA exhibited the lowest PE inset contact stress under stance phase gait cycle, followed by AMC UKA and FC UKA. Under the squat loading conditions, CC 3. Results UKA exhibited the lowest PE insert contact stress. During the swing phase, CC UKA exhibited the highest PE inset 3.1. Intact Model Validation. The intact FE model was compared to the experiment using the Fe model’s subject contact stress, followed by AMC UKA and FC UKA. for validation purposes. Under the loading condition with a Figure 5 shows the contact stress on the lateral meniscus 30 flexion, the anterior tibial translation was 2.83 mm in for different tibial insert designs and a native knee joint under the experiment and 2.54 mm in the FE model, and the poste- gait and squat loading conditions. Contact stress on the lat- eral meniscus in the native knee was higher than that in the rior tibial translation was 2.12 mm in the experiment and 2.18 mm in the FE model. At 90 flexion, the anterior tibial three different tibial insert designs for the customized UKA translation was 3.32 mm in the experiment and 3.09 mm in during the stance phase gait cycle. The trend of contact stress the FE model, and the posterior tibial translation was on the lateral meniscus was also observed under deep flexion 2.64 mm in the experiment and 2.71 mm in the FE model. squat loading conditions. The lateral meniscus, like the PE The experimental results show good agreement with those insert, exhibited high contact stress during the stance phase obtained using the FE model [19]. Furthermore, the intact and low contact stress during the swing phase for the three FE model was validated by comparing it with computational different tibial insert designs for the customized UKA, com- pared to the native knee. results from previous studies. Under an axial load of 1,150 N, average contact stresses of 3.1 MPa and 1.53 MPa were Figure 6 shows the contact stress on the articular cartilage for the three different tibial insert designs for the customized observed on the medial and lateral menisci, respectively. Both are within 6% of the 2.9 MPa and 1.45 MPa contact UKA under gait and squat loading conditions. During the stress values reported by Pena et al. [29]. These minor gait cycle, contact stress on the articular cartilage in the native knee was lower than that in the three different tibial differences may be due to geometrical variations between Contract stress on PE insert (MPa) Contract stress on PE insert (MPa) Applied Bionics and Biomechanics 5 10 10 9 9 8 8 7 7 6 6 5 5 4 4 3 3 2 2 1 1 0 0 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 Gait cycle (%) Squat loading (%) FC UKA CC UKA FC UKA CC UKA AMC UKA Native knee AMC UKA Native knee (a) (b) Figure 5: Comparison of the contact stress on the lateral meniscus in three customized UKA designs with three different conformities against that on a native knee under (a) gait and (b) squat loading conditions. 4.5 4.5 4 4 3.5 3.5 3 3 2.5 2.5 2 2 1.5 1.5 1 1 0.5 0.5 0 0 0 10 20 30 40 50 60 70 80 90 100 0 10 20 30 40 50 60 70 80 90 100 Gait cycle (%) Squat loading (%) FC UKA CC UKA FC UKA CC UKA AMC UKA Native knee AMC UKA Native knee (a) (b) Figure 6: Comparison of the contact stress on the articular cartilage in three customized UKA designs with three different conformities against that on a native knee under (a) gait and (b) squat loading conditions. follow-up duration of ten years, medial UKA is associated insert designs for the customized UKA. FC UKA and CC UKA exhibited higher contact stress on the articular cartilage with excellent clinical and radiographic results [38]. than on the native knee in the swing phase. Furthermore, the Although the ten-year survival rate is excellent, radiographic CC UKA exhibited higher contact stress on the articular car- signs of progression of OA were observed in the other com- tilage than on the native knee under high flexion squat load- partments [38]. Theoretically, UKA requires a technically demanding procedure and precise component positioning ing conditions. Under gait and squat loading conditions, the contact stress on the lateral meniscus and articular cartilage [6, 39]. Furthermore, UKA entails challenges due to surgical indicates that the AMC UKA is closest to normal contact difficulties, such as device failures, residual pain, subsidence, mechanics. and OA progression in the other compartments [38, 40]. To overcome this problem, a customized instrumentation tech- nique is applied to UKA. 4. Discussion Bell et al. evaluated the accuracy and clinical outcomes of The most important finding of this study is that the AMC the customized instrumentation implementation technique UKA exhibits close to native knee contact mechanics. There- using a fixed-bearing UKA [41]. They proved that the tech- fore, the AMC UKA prevents progressive OA of other nique might offer specific advantages to surgeons who per- form lower volumes of UKA and can potentially improve compartments. We evaluated contact stress, which is closely related both clinical outcomes and implant survivorship of UKA to degenerative OA of the knee joint after medial UKA and achieve greater consistency in results [41]. However, it [36, 37]. A previous study indicates that after a minimum is not possible for this type of customized instrumentation Contract stress on lateral meniscus (MPa) Contract stress on lateral meniscus (MPa) Contract stress on articular cartilage (MPa) Contract stress on lateral meniscus (MPa) 6 Applied Bionics and Biomechanics On the lateral side, the cartilage layer of the TF exhibits to resolve the effect of morphology with respect to ethnicity and gender differences. The Asian population exhibits a an elastic modulus of 15 MPa. In contrast to the cartilage smaller build and stature compared to the Western popula- layers, the tibial articular insert exhibits an elastic modulus of 685 MPa. Consequently, the material characteristics of tion [12]. A majority of conventional UKA prostheses are designed to match the Caucasian physique [42]. In UKA, the medial and lateral compartments differ by more than 40 the geometry of the femoral and tibial components should times. Notably, other compartments in the AMC UKA have match the resected surface to the maximum extent possible the advantage of contact mechanics similar to that of the to provide optimal stability and load transfer [42]. Koeck native knee in swing phase gait and high flexion. CC UKA and FC UKA showed kinematic change, which led to lateral et al. indicated that customized instrumentation and implant using fixed-bearing UKA can reliably restore the leg axis, cartilage contact stress because they did not restore tibial obtain a medial proximal tibial angle of 90 insert conformity and native anatomy. This trend was found , prevent implant malpositioning, and ensure maximal tibial coverage [43]. for swing phase gait and high flexion squat loading condi- Steklov et al. indicated that a constant coronal curvature tions. The most important advantage of the AMC UKA was observed under high flexion where the effect of the anatomy can be applied to a customized UKA by measuring coronal curvatures across the femoral condyle in each patient and mimetic tibial insert was visible as the J curve of the femur by deriving the average curvature [18]. This novel approach was maintained in the femoral component. combines the unique benefits of customized geometry with The contact area is most important during the stance proven design concepts in UKA to minimize PE wear [18]. phase gait cycle and deep flexion during squat loading condi- tions, during which the axial force was primarily visible. However, as previously mentioned, the customized UKA should overcome edge loading at select flexion angles when However, the contact area, as well as the kinematics, is also a curved tibial insert is used [17]. To address the problem, a crucial during the swing phase gait cycle and high flexion flat PE tibial insert is paired with the constant coronal curva- under squat loading conditions. Unfortunately, both the ture femoral component, and this ensures constant loading femur and tibial mimetic AMC UKAs could not preserve perfect normal knee contact mechanism. An important fac- conditions over a large area, irrespective of the flexion angle [17, 18]. However, in a native knee, the medial and lateral tib- tor is that change in the mechanism due to change in material ial plateaus exhibit anatomical asymmetric geometries with a stiffness plays the most crucial role, even if it corresponds to slightly dished medial plateau and a convex lateral plateau. an anatomy mimetic design. Furthermore, the tibial insert The result presents the pattern of various contact stresses could not perfectly replicate the role of mobile meniscus characteristics. Generally, there are significant differences on the PE tibial insert and other compartments in the cus- tomized UKA with respect to different tibial insert designs. between the biomechanics of the medial and lateral menisci An interesting finding was observed in CC UKA: the CC [45, 46]. The medial meniscus is significantly less mobile than the lateral meniscus due to its attachment to the medial UKA exhibited increased contact stress on the PE insert dur- ing the swing phase gait cycle and high flexion during squat collateral ligament and larger insertion areas. In terms of clinical relevance, it is not possible to apply a loading conditions. The most influential factor on contact stress is the contact area. Therefore, the CC UKA with an conforming design to the tibial insert when a customized increased contact area should exhibit decreased contact UKA is developed. Bernasek et al. reported unsatisfactory stress, although it did not exhibit this. Generally, conforming results regarding the insertion of the same type of conform- design is used in the mobile-bearing UKA [36]. However, in ing fixed-bearing UKA [47]. Furthermore, a previous study this study, the conforming design was used in the fixed- indicated that significant degenerative changes in the other bearing UKA. Abnormal kinematics and increased contact compartments occurred in only one of the eighty-seven stress were observed, and this was similar for the swing phase knees in which an unconstrained UKA was implanted [48]. and high flexion. When flexion increased, for the CC UKA, The results support the reliability of this study. The AMC movement of the tibial insert restores a similar contact area. UKA should apply mobile characteristics to the tibial insert However, edge loading may occur in a fixed condition. For to preserve knee mechanics closer to that of the native knee. the stance phase gait and deep flexion under squat loading However, a reason for the application of the conforming conditions in which the flexion angle does not show a signif- design to mobile-bearing UKA involves preventing bearing icant effect, the CC UKA exhibited the lowest contact stress dislocation. Therefore, a spinout mechanism should be con- due to the advantage of conformity. sidered for preventing dislocation through the application In the lateral meniscus, a trend of contact stress simi- of mobile characteristics in the AMC UKA to preserve native lar to that in the PE insert was observed in the customized knee mechanics. UKA for the three different tibial insert designs. This Two strengths of this study are as follows: First, unlike trend is probably due to the role the menisci play in pro- previous UKA studies, the FE model included the tibia, tecting the TF cartilage layers when the load is transferred. femur, and related soft tissues [49, 50]. Second, unlike the When the UKA was implanted, the contact stress on the current biomechanical UKA model, this study included the lateral meniscus is lower than that in the native knee dur- application of gait and squat loading conditions [49, 50]. ing the stance phase of the gait cycle in which loading is Nevertheless, several limitations should also be noted. mainly involved. This is primarily due to the change in First, the bony structures were assumed as rigid, while in real- stiffness between the medial and lateral compartments ity, bone exhibits cortical and cancellous tissues. However, induced in the knee by the device [44]. the primary purpose of the study did not involve evaluating Applied Bionics and Biomechanics 7 the effects of different prostheses on bone. Furthermore, the States,” The Journal of Arthroplasty, vol. 23, no. 3, pp. 408– 412, 2008. assumption exerted minimal influence on the study because the stiffness of bone exceeds that of the relevant soft tissues [3] J.-P. Whittaker, D. D. R. Naudie, J. P. McAuley, R. W. McCalden, S. J. MacDonald, and R. B. Bourne, “Does bear- [29]. Second, the computational model represented a cus- ing design influence midterm survivorship of unicompart- tomized UKA and the results are not necessarily expected mental arthroplasty?,” Clinical Orthopaedics and Related to extend to other implant designs, such as the customized Research, vol. 468, no. 1, pp. 73–81, 2010. mobile-bearing UKA. Third, the material properties and [4] K. G. Vince and L. T. Cyran, “Unicompartmental knee attachment points of the ligaments were assumed in the arthroplasty: new indications, more complications?,” The Jour- model based on values from extant studies, although signifi- nal of Arthroplasty, vol. 19, 4 Suppl 1, pp. 9–16, 2004. cant variability exists regarding reported values. However, [5] G. C. R. Keene and M. C. Forster, “(iii) Modern unicompart- the objective did not involve determining the actual values mental knee replacement,” Current Orthopaedics, vol. 19, of ligament forces but determining the effect of variability no. 6, pp. 428–445, 2005. in a customized fixed-bearing UKA with respect to the tibial [6] F. Zambianchi, V. Digennaro, A. Giorgini et al., “Surgeon’s insert design corresponding to the femoral component. Fur- experience influences UKA survivorship: a comparative study thermore, the advantage of computer simulation of a single between all-poly and metal back designs,” Knee surgery, sports subject is that we could determine the effects of the tibial traumatology, arthroscopy : official journal of the ESSKA, insert design of a customized UKA within the same individ- vol. 23, no. 7, pp. 2074–2080, 2015. ual and eliminate the effects of other variables, such as [7] W. Fitz, “Unicompartmental knee arthroplasty with use of weight, height, bony geometry, ligament properties, and novel patient-specific resurfacing implants and personalized component size [51]. jigs,” The Journal of bone and joint surgery American volume, vol. 91, Supplement 1, pp. 69–76, 2009. 5. Conclusion [8] J. Hashemi, N. Chandrashekar, B. Gill et al., “The geometry of the tibial plateau and its influence on the biomechanics of the The anatomy mimetic design, which retains the native tibial tibiofemoral joint,” The Journal of bone and joint surgery insert, exhibited significant contact mechanics improvement American volume, vol. 90, no. 12, pp. 2724–2734, 2008. over the customized UKA during gait and squat loading [9] E. Servien, M. Saffarini, S. Lustig, S. Chomel, and P. Neyret, conditions. The nonanatomic tibial insert geometry of the “Lateral versus medial tibial plateau: morphometric analysis customized UKA contributed to contact mechanics abnor- and adaptability with current tibial component design,” Knee malities, including the PE tibial insert and the other compart- surgery, sports traumatology, arthroscopy : official journal of ments. Therefore, the AMC UKA may represent an essential the ESSKA, vol. 16, no. 12, pp. 1141–1145, 2008. step in our attempt to restore the function of the native [10] K. R. Berend, A. V. Lombardi Jr., T. H. Mallory, J. B. Adams, mechanics of the knee. Based on the results for the femoral and K. L. Groseth, “Early failure of minimally invasive uni- component as well as the tibial insert in a customized UKA, compartmental knee arthroplasty is associated with obesity,” Clinical Orthopaedics and Related Research, vol. 440, no. &NA;, the anatomy mimetic design preserves normal knee biome- pp. 60–66, 2005. chanics and thus may prevent progressive osteoarthritis of [11] K. R. Berend, A. V. Lombardi Jr., and J. B. Adams, “Obesity, the other compartments. young age, patellofemoral disease, and anterior knee pain: identifying the unicondylar arthroplasty patient in the United Data Availability States,” Orthopedics, vol. 30, no. 5, pp. 19–23, 2007. [12] S. V. Vaidya, C. S. Ranawat, A. Aroojis, and N. S. Laud, The data used to support the findings of this study are “Anthropometric measurements to design total knee prosthe- included within the article. ses for the Indian population,” The Journal of Arthroplasty, vol. 15, no. 1, pp. 79–85, 2000. Conflicts of Interest [13] K. T. Kang, J. Son, O. R. Kwon et al., “Morphometry of femoral rotation for total knee prosthesis according to gen- The authors declare that there is no conflict of interests der in a Korean population using three-dimensional mag- regarding the publication of this paper. netic resonance imaging,” The Knee, vol. 23, no. 6, pp. 975–980, 2016. Authors’ Contributions [14] K. T. Kang, J. Son, O. R. Kwon et al., “Effects of measurement methods for tibial rotation axis on the morphometry in Yong-Gon Koh and Kyoung-Mi Park contributed equally to Korean populations by gender,” The Knee, vol. 24, no. 1, this work and should be considered co-first authors. pp. 23–30, 2017. [15] ConforMIS, Inc, Novemver 2019, https://www.conformis.com. References [16] D. P. Carpenter, R. R. Holmberg, M. J. Quartulli, and C. L. Barnes, “Tibial plateau coverage in UKA: a comparison of [1] A. Carr, G. Keyes, R. Miller, J. O'Connor, and J. Goodfellow, “Medial unicompartmental arthroplasty. A survival study of patient specific and off-the- shelf implants,” The Journal of Arthroplasty, vol. 29, no. 9, pp. 1694–1698, 2014. the Oxford meniscal knee,” Clinical Orthopaedics and Related Research, vol. 295, pp. 205–213, 1993. [17] K. T. Kang, J. Son, D. S. Suh, S. K. Kwon, O. R. Kwon, and Y. G. [2] D. L. Riddle, W. A. Jiranek, and F. J. McGlynn, “Yearly inci- Koh, “Patient-specific medial unicompartmental knee arthro- dence of unicompartmental knee arthroplasty in the United plasty has a greater protective effect on articular cartilage in 8 Applied Bionics and Biomechanics arthroplasty using computational simulation,” Bone & joint the lateral compartment: a finite element analysis,” Bone & joint research, vol. 7, no. 1, pp. 20–27, 2018. research, vol. 5, no. 11, pp. 552–559, 2016. [32] I. Kutzner, B. Heinlein, F. Graichen et al., “Loading of the knee [18] N. Steklov, J. Slamin, S. Srivastav, and D. D’Lima, “Unicom- partmental knee resurfacing: enlarged tibio-femoral contact joint during activities of daily living measured _in vivo_ in five subjects,” Journal of Biomechanics, vol. 43, no. 11, pp. 2164– area and reduced contact stress using novel patient-derived geometries,” Open Biomedical Engineering Journal, vol. 4, 2173, 2010. pp. 85–92, 2010. [33] J. P. Halloran, C. W. Clary, L. P. Maletsky, M. Taylor, A. J. Petrella, and P. J. Rullkoetter, “Verification of predicted [19] K. T. Kang, S. H. Kim, J. Son, Y. H. Lee, and Y. G. Koh, “Val- knee replacement kinematics during simulated gait in the idation of a computational knee joint model using an align- Kansas knee simulator,” Journal of biomechanical engineering, ment method for the knee laxity test and computed vol. 132, no. 8, p. 081010, 2010. tomography,” Bio-medical Materials and Engineering, vol. 28, no. 4, pp. 417–429, 2017. [34] K. T. Kang, Y. G. Koh, J. Son et al., “Finite element analysis of the biomechanical effects of 3 posterolateral corner [20] K. T. Kang, S. K. Kwon, J. Son, O. R. Kwon, J. S. Lee, and Y. G. reconstruction techniques for the knee joint,” Arthroscopy : Koh, “The increase in posterior tibial slope provides a positive the journal of arthroscopic & related surgery : official publica- biomechanical effect in posterior-stabilized total knee arthro- tion of the Arthroscopy Association of North America and the plasty,” Knee Surgery, Sports Traumatology, Arthroscopy, International Arthroscopy Association, vol. 33, no. 8, vol. 26, no. 10, pp. 3188–3195, 2018. pp. 1537–1550, 2017. [21] Y. G. Koh, K. M. Park, H. Y. Lee, and K. T. Kang, “Influ- [35] E. S. Grood and W. J. Suntay, “A joint coordinate system for ence of tibiofemoral congruency design on the wear of the clinical description of three-dimensional motions: applica- patient-specific unicompartmental knee arthroplasty using tion to the knee,” Journal of Biomechanical Engineering, finite element analysis,” Bone & joint research, vol. 8, no. 3, vol. 105, no. 2, pp. 136–144, 1983. pp. 156–164, 2019. [36] O. R. Kwon, K. T. Kang, J. Son et al., “Biomechanical compar- [22] D. J. Van Den Heever, C. Scheffer, P. J. Erasmus, and E. M. ison of fixed‐ and mobile‐bearing for unicomparmental knee Dillon, “Contact stresses in a patient-specific unicompart- arthroplasty using finite element analysis,” Journal of Ortho- mental knee replacement,” in Proceedings of the 2010 paedic Research : Official Publication of the Orthopaedic Annual International Conference of the IEEE Engineering Research Society, vol. 32, no. 2, pp. 338–345, 2014. in Medicine and Biology Society (EMBC 2010), pp. 5113– [37] N. A. Segal, D. D. Anderson, K. S. Iyer et al., “Baseline articular 5116, Buenos Aires, Argentina, 2010. contact stress levels predict incident symptomatic knee osteo- [23] W. B. Kurtz, J. E. Slamin, and S. W. Doody, “Bone preservation arthritis development in the MOST cohort,” Journal of Ortho- in a novel patient specific total knee replacement,” Reconstruc- paedic Research : Official Publication of the Orthopaedic tive Review, vol. 6, no. 1, pp. 23–29, 2016. Research Society, vol. 27, no. 12, pp. 1562–1568, 2009. [24] C. Fitzpatrick, D. FitzPatrick, J. Lee, and D. Auger, “Statistical [38] R. A. Berger, R. Michael Meneghini, J. J. Jacobs et al., “Results design of unicompartmental tibial implants and comparison of unicompartmental knee arthroplasty at a minimum of ten with current devices,” The Knee, vol. 14, no. 2, pp. 138–144, years of follow-up,” The Journal of bone and joint surgery American volume, vol. 87, no. 5, pp. 999–1006, 2005. [25] M. K. Harman, S. Schmitt, S. Rössing et al., “Polyethylene [39] M. H. Liow, T. Y. Tsai, D. Dimitriou, G. Li, and Y. M. Kwon, damage and deformation on fixed-bearing, non-conforming “Does 3-dimensional in vivo component rotation affect clini- unicondylar knee replacements corresponding to progressive cal outcomes in Unicompartmental knee arthroplasty?,” The changes in alignment and fixation,” Clinical Biomechanics Journal of Arthroplasty, vol. 31, no. 10, pp. 2167–2172, 2016. (Bristol, Avon), vol. 25, no. 6, pp. 570–575, 2010. [40] A. Lindstrand, A. Stenstrom, and S. Lewold, “Multicenter [26] L. Blankevoort and R. Huiskes, “Validation of a three- study of unicompartmental knee revision. PCA, Marmor, dimensional model of the knee,” Journal of Biomechanics, and St Georg compared in 3,777 cases of arthrosis,” Acta vol. 29, no. 7, article 0021929095001492, pp. 955–961, 1996. Orthopaedica Scandinavica, vol. 63, no. 3, pp. 256–259, 1992. [27] K. F. Bowman Jr. and J. K. Sekiya, “Anatomy and biomechan- [41] S. W. Bell, J. Stoddard, C. Bennett, and N. J. London, “Accu- ics of the posterior cruciate ligament, medial and lateral sides racy and early outcomes in medial unicompartmental knee of the knee,” Sports Medicine and Arthroscopy Review, arthroplasty performed using patient specific instrumenta- vol. 18, no. 4, pp. 222–229, 2010. tion,” The Knee, vol. 21, Supplemenrt 1, pp. S33–S36, 2014. [28] J. L. Baldwin, “The anatomy of the medial patellofemoral liga- [42] S. Surendran, D. S. Kwak, U. Y. Lee et al., “Anthropometry of ment,” The American Journal of Sports Medicine, vol. 37, the medial tibial condyle to design the tibial component for no. 12, pp. 2355–2361, 2009. unicondylar knee arthroplasty for the Korean population,” [29] E. Peña, B. Calvo, M. A. Martinez, D. Palanca, and M. Doblaré, Knee surgery, sports traumatology, arthroscopy, vol. 15, no. 4, “Why lateral meniscectomy is more dangerous than medial pp. 436–442, 2007. meniscectomy. A finite element study,” Journal of Orthopaedic [43] F. X. Koeck, J. Beckmann, C. Luring, B. Rath, J. Grifka, and Research : Official Publication of the Orthopaedic Research E. Basad, “Evaluation of implant position and knee alignment Society, vol. 24, no. 5, pp. 1001–1010, 2006. after patient-specific unicompartmental knee arthroplasty,” [30] A. Godest, M. Beaugonin, E. Haug, M. Taylor, and P. J. Greg- The Knee, vol. 18, no. 5, pp. 294–299, 2011. son, “Simulation of a knee joint replacement during a gait cycle [44] K. T. Kang, O. R. Kwon, J. Son, D. S. Suh, S. K. Kwon, and Y. G. using explicit finite element analysis,” Journal of Biomechanics, Koh, “Effect of joint line preservation on mobile-type bearing vol. 35, no. 2, pp. 267–275, 2002. unicompartmental knee arthroplasty: finite element analysis,” [31] K. T. Kang, Y. G. Koh, J. Son et al., “Measuring the effect of Australasian Physical & Engineering Sciences in Medicine, femoral malrotation on knee joint biomechanics for total knee vol. 41, no. 1, pp. 201–208, 2018. Applied Bionics and Biomechanics 9 [45] A. J. Fox, A. Bedi, and S. A. Rodeo, “The basic science of human knee menisci: structure, composition, and function,” Sports health, vol. 4, no. 4, pp. 340–351, 2012. [46] I. D. McDermott, S. D. Masouros, and A. A. Amis, “Biome- chanics of the menisci of the knee,” Current Orthopaedics, vol. 22, no. 3, pp. 193–201, 2008. [47] T. L. Bernasek, J. A. Rand, and R. S. Bryan, “Unicompartmen- tal porous coated anatomic total knee arthroplasty,” Clinical Orthopaedics and Related Research, vol. 236, pp. 52–59, 1988. [48] W. A. Hodge and H. P. Chandler, “Unicompartmental knee replacement: a comparison of constrained and unconstrained designs,” The Journal of bone and joint surgery American vol- ume, vol. 74, no. 6, pp. 877–883, 1992. [49] S. Inoue, M. Akagi, S. Asada, S. Mori, H. Zaima, and M. Hashida, “The valgus inclination of the tibial component increases the risk of medial tibial condylar fractures in unicompartmental knee arthroplasty,” The Journal of Arthroplasty, vol. 31, no. 9, pp. 2025–2030, 2016. [50] E. C. Pegg, J. Walter, S. J. Mellon et al., “Evaluation of factors affecting tibial bone strain after unicompartmental knee replacement,” Journal of Orthopaedic Research : Official Publication of the Orthopaedic Research Society, vol. 31, no. 5, pp. 821–828, 2013. [51] K. T. Kang, Y. G. Koh, J. Son, O. R. Kwon, J. S. Lee, and S. K. Kwon, “Influence of increased posterior tibial slope in total knee arthroplasty on knee joint biomechanics: a computa- tional simulation study,” The Journal of Arthroplasty, vol. 33, no. 2, pp. 572–579, 2018. International Journal of Advances in Rotating Machinery Multimedia Journal of The Scientific Journal of Engineering World Journal Sensors Hindawi Hindawi Publishing Corporation Hindawi Hindawi Hindawi Hindawi www.hindawi.com Volume 2018 http://www www.hindawi.com .hindawi.com V Volume 2018 olume 2013 www.hindawi.com Volume 2018 www.hindawi.com Volume 2018 www.hindawi.com Volume 2018 Journal of Control Science and Engineering Advances in Civil Engineering Hindawi Hindawi www.hindawi.com Volume 2018 www.hindawi.com Volume 2018 Submit your manuscripts at www.hindawi.com Journal of Journal of Electrical and Computer Robotics Engineering Hindawi Hindawi www.hindawi.com Volume 2018 www.hindawi.com Volume 2018 VLSI Design Advances in OptoElectronics International Journal of Modelling & Aerospace International Journal of Simulation Navigation and in Engineering Engineering Observation Hindawi Hindawi Hindawi Hindawi Volume 2018 Volume 2018 Hindawi www.hindawi.com Volume 2018 www.hindawi.com Volume 2018 www.hindawi.com www.hindawi.com www.hindawi.com Volume 2018 International Journal of Active and Passive International Journal of Antennas and Advances in Chemical Engineering Propagation Electronic Components Shock and Vibration Acoustics and Vibration Hindawi Hindawi Hindawi Hindawi Hindawi www.hindawi.com Volume 2018 www.hindawi.com Volume 2018 www.hindawi.com Volume 2018 www.hindawi.com Volume 2018 www.hindawi.com Volume 2018

Journal

Applied Bionics and BiomechanicsHindawi Publishing Corporation

Published: Nov 14, 2019

References