Differences in impact on adjacent compartments in medial unicompartmental knee arthroplasty versus high tibial osteotomy with identical valgus alignment

BackgroundIt is unclear why medial unicompartmental knee arthroplasty (UKA) with postoperative valgus alignment causes adjacent compartment osteoarthritis more often than high tibial osteotomy (HTO) for moderate medial osteoarthritis of the knee with varus deformity. This study used a computer simulation to evaluate differences in knee conditions between UKA and HTO with identical valgus alignment.MethodsDynamic musculoskeletal computer analyses of gait were performed. The hip–knee–ankle angle in fixed-bearing UKA was changed from neutral to 7° valgus by changing the tibial insert thickness. The hip–knee–ankle angle in open-wedge HTO was also changed from neutral to 7° valgus by opening the osteotomy gap.ResultsThe lateral tibiofemoral contact forces in HTO were larger than those in UKA until moderate valgus alignments. However, the impact of valgus alignment on increasing lateral forces was more pronounced in UKA, which ultimately demonstrated a larger lateral force than HTO. Valgus alignment in UKA caused progressive ligamentous tightness, including that of the anterior cruciate ligament, resulting in compression of the lateral tibiofemoral compartment. Simultaneously, patellofemoral shear forces were slightly increased and excessive external femoral rotation against the tibia occurred due to the flat medial tibial insert surface and decreased lateral compartment congruency. By contrast, only lateral femoral slide against the tibia occurred in excessively valgus-aligned HTO.ConclusionsIn contrast to extra-articular correction in HTO, which results from opening the osteotomy gap, intra-articular valgus correction in UKA with thicker tibial inserts caused progressive ligamentous tightness and kinematic abnormalities, resulting in early osteoarthritis progression into adjacent compartments.     

In vivo kinematic comparison before and after mobile-bearing unicompartmental knee arthroplasty during high-flexion activities

BackgroundMany patients who undergo unicompartmental knee arthroplasty (UKA) have an expectation that their knee flexion would increase following its replacement. Additionally, the survival rate of mobile-bearing UKA (MB-UKA) is high. However, the effect on the patient's kinematics remains unknown. This study aimed to clarify the kinematic effect of MB-UKA knees during high-flexion activities by comparing the in vivo kinematics before and after surgery.MethodsA squatting motion was performed under fluoroscopic surveillance in the sagittal plane before and after MB-UKA. To estimate the spatial position and orientation of the knee, a two-dimensional/three-dimensional registration technique was used. The femoral rotation and varus–valgus angle relative to the tibia and anteroposterior (AP) translation of the medial and lateral side of the femur on the plane perpendicular to the tibial mechanical axis in each flexion angle were evaluated.ResultsRegarding the varus–valgus angle, the preoperative knees indicated a significant varus alignment compared with the postoperative knees from 10° to 60° of flexion. There were no significant differences in the femoral rotation angle, AP translation, and kinematic pathway before and after MB-UKA in the mid-flexion of the range of motion.ConclusionThere were differences between the varus–valgus knee kinematics before and after MB-UKA, from 10 to 60° of flexion, but no difference from midrange of flexion to deep flexion. In addition, the rotational knee kinematics before and after MB-UKA was not significantly different.     

UKA 关节线安装误差对膝关节接触力学和运动学影响

目的 针对单髁膝关节置换(unicompartmental knee arthroplasty, UKA)内侧假体松动和外侧关节软骨退化问题,通过骨肌多体动力学方法研究不同生理活动中UKA关节线安装误差对膝关节接触力学和运动学的影响。方法 以内侧自然关节线为0 mm误差,分别考虑±2 mm、±4 mm、±6 mm共6种关节线安装误差情况,建立7个内侧UKA置换的骨肌多体动力学模型,对比研究步行和下蹲运动中膝关节接触力学和运动学的变化。结果 在步行步态周期70%时,相比于0 mm误差UKA假体关节线升高2 mm时内侧假体接触力增大127.3%,外侧软骨接触力减少12.0%;在UKA假体关节线降低4 mm时内侧假体接触力接近0 N,外侧软骨接触力增大10.1%;胫股关节总接触力在关节线升高和降低2 mm时分别增大19.7%和减小14.2%。在下蹲屈膝100°时,相比于0 mm误差膝关节内侧假体接触力和胫股骨关节总接触力在UKA假体关节线升高2 mm时分别增大31.6%和11.1%,在UKA假体关节线降低2 mm时分别减小24.5%和8.5%,而膝关节外侧软骨接触力变化不大。同时,在步行步态...     

Comparison of medial and lateral posterior femoral condyle articular cartilage wear patterns

Background

While degenerative changes to the articular cartilage of the anterior and distal portions of the femoral condyles have been well studied in the literature, the changes that occur on the posterior femoral condyle are not as clear. The purpose of this study was to assess the difference in articular cartilage thickness between the medial and lateral posterior femoral condyles in knees undergoing unicompartmental knee arthroplasty.

膝关节单髁置换术胫骨假体不同后倾角对假体磨损和功能的影响

目的 建立单髁置换术胫骨假体后倾3°和7°膝关节不同屈膝角度三维有限元模型,研究两种后倾角膝关节生物力学特性和假体磨损及其对功能的影响.方法 结合人体膝关节CT与MRI图像和第3代Oxford假体,建立胫骨假体后倾3°和7°下屈膝单髁置换术有限元模型,在股骨内外侧髁中心点上施加1 kN载荷模拟人体站立相负重,分析不同屈...     

MRI-determined preoperative lateral meniscus degeneration is not associated with adverse mid-term clinical results after mobile-bearing unicompartmental knee arthroplasty

BackgroundOne of the conditions constituting surgical indication for medial mobile-bearing unicompartmental knee arthroplasty (UKA) is that there is full-thickness cartilage in the lateral compartment under valgus stress radiography. However, it is unclear whether medial unicompartmental knee arthroplasty should be performed if there is degeneration of the lateral meniscus on preoperative magnetic resonance imaging (MRI).MethodsThe records of 77 patients (77 knees) who underwent Oxford mobile-bearing UKA were retrospectively reviewed. Based on the status of the lateral meniscus in each knee using preoperative MRI with Stoller's classification system, the patients were divided into two groups; a normal group and a lateral meniscus degenerated group (grades 1–3). The preoperative personal data and the outcome data three years postoperatively were compared.ResultsThe normal group contained 31 knees while the lateral meniscus degenerated group comprised 46 knees. There was no difference in clinical outcome or knee function between the groups at three years after UKA. There was no difference in re-operation and revision rate between the groups with no revisions in either group.ConclusionsIt may not be necessary to exclude UKA indications for cases with degenerative findings in the lateral meniscus on preoperative MRI.     

单髁置换术应用于骨关节炎合并前交叉韧带缺失的三维有限元研究

目的采用有限元方法比较前交叉韧带(anterior cruciate ligament,ACL)完整与缺失的骨关节炎患者单髁关节置换(unicompartmental knee arthroplasty,UKA)术后膝关节生物力学特性,分析ACL缺失对膝关节单髁置换术后的运动和应力的影响。方法根据膝关节CT、MRI图像,建立有限元模型。采用逆向工程技术重建活动衬垫单髁假体,加载入该正常膝关节三维有限元模型。在不同屈膝角度(0°、30°、60°、90°、120°)加载载荷,观察在ACL完整(ACL-intact,ACLI)和缺失(ACL-deficiency,ACLD)情况下,膝关节的最大接触压和位移程度。结果 UKA-ACLI与UKA-ACLD模型在膝关节屈膝各角度,各部位(外侧股骨软骨、胫骨软骨、半月板、股骨假体、胫骨假体、衬垫)最大应力无明显差异,ACLD模型在膝关节屈膝0°和30°位前后位移明显大于ACLI模型,在膝关节屈膝0°位股骨相对内旋减小,在膝关节屈膝30°位股骨相对外旋增加。结论标准位置假体植入情况下,ACL缺失并不会导致UKA术后应力异常增大,会导致在膝关节伸直位时位移增加。     

Finite element analysis of the influence of the posterior tibial slope on mobile-bearing unicompartmental knee arthroplasty

BackgroundThe most common modes of failure reported in unicompartmental knee arthroplasty (UKA) in its first two decades were wear on the polyethylene (PE) insert, component loosening, and progressive osteoarthritis in the other compartment. The rates of implant failure due to poor component positioning in patients who have undergone UKA have been reported. However, the effect of the posterior tibial slope on the biomechanical behavior of mobile-bearing Oxford medial UKA remains unknown.MethodsWe applied finite element (FE) analysis to evaluate the effects of the posterior tibial slope in mobile-bearing UKA on the contact stresses in the superior and inferior surfaces of PE inserts and articular cartilage as well as the forces exerted on the anterior cruciate ligament (ACL). Seven FE models for posterior tibial slopes of −1°, 1°, 3°, 5°, 7°, 9°, and 11° were developed and analyzed under normal-level walking conditions based on this approach.ResultsThe maximum contact stresses on both the superior and inferior surfaces of the PE insert decreased as the posterior tibial slope increased. However, the maximum contact stress on the lateral articular cartilage and the force exerted on the ACL increased as the posterior tibial slope increased.ConclusionsIncreasing the tibial slope led to a reduction in the contact stress on the PE insert. However, a high contact stress on the other compartment and increased ACL force can cause progressive osteoarthritis in the other compartment and failure of the ACL.     

How does the inclination of the tibial component matter? A three-dimensional finite element analysis of medial mobile-bearing unicompartmental arthroplasty

Background

Medial unicompartmental knee arthroplasty (UKA) using Oxford mobile-bearing prosthesis is performed in the treatment of medial compartmental arthritis of the knee. However, little is known about the stress distributions for mobile-bearing UKA on the medial tibial plateau.

The effect of component alignment on clinical outcomes in fixed bearing unicompartmental knee arthroplasty

BackgroundThe aim of this study is to report component alignment in a series of ZUK fixed bearing unicompartmental knee arthroplasty (UKA) implants and compare this to clinical outcomes.MethodsThe radiographs, Knee Society Scores (KSS) and knee flexion of 223 medial UKAs were evaluated. The following alignment parameters were assessed; coronal and sagittal femoral component angle (c-FCA and s-FCA), coronal and sagittal tibia component angle (c-TCA and s-TCA) and the coronal tibiofemoral angle (c-TFA). Each alignment parameter was grouped at consecutive 2.5° intervals, mean KSS and knee flexion was then compared between the interval groups.Results96.4% of femoral components were between 7.5° of varus and valgus and 95.1% between 7.5° extension and 5° flexion. 89.6% of tibial components were between 7.5° of varus and 2.5° valgus and 97.3% between 2.5° and 15° flexion. There was no significant difference between the KSS or knee flexion between any of the incremental groups of component alignment. Mean c-TFA was 0.2 ± 3.0°, 92.4% were between −5° (varus) and 5° (valgus). KSS were significantly greater for two of the increments with slightly more varus. Linear regression analysis showed there was very weak correlation (R² = 0.1933) between c-TFA and c-TCA.ConclusionsThe results of this study show that fixed bearing UKA components are forgiving to accommodate some variation in tibial and femoral component position without effecting clinical outcome scores or knee flexion. Limb alignment matters more than component position and knees with slight varus tibiofemoral alignment have better clinical scores than those with valgus.     

Medium term results of per-operative knee arthroscopy in confirming suitability for unicompartmental arthroplasty

IntroductionThe status of the lateral compartment of the knee is a determining factor in the long-term outcome of medial unicompartmental arthroplasty (UKA). Various methods of assessing the lateral compartment have been used including stress radiography, radioisotope bone scanning, magnetic resonance imaging and visualisation at the time of surgery. Arthroscopy is another means of directly assessing the integrity of the articular cartilage and the meniscus in the lateral compartment.PurposeThis study aims to show that per-operative arthroscopy is a safe and effective means of deciding whether to proceed with UKA or convert to total knee arthroplasty (TKA).MethodWe have used arthroscopy of the lateral compartment to assess suitability for UKA in 151 knees over 8 years.ResultsAt time of arthroscopy 34 knees underwent a change of surgical plan from UKA to TKA (22.5%). There has been one revision to TKA and 2 bearing exchanges for dislocation.ConclusionImmediate per-operative arthroscopy is a reliable method for assessing the suitability of a knee for UKA, in particular the lateral compartment.     

基于CT和MRI膝关节有限元模型建立与不同载荷下生物力学特性分析

基于CT和MRI图像数据建立膝关节有限元模型,采用六面体网格对不同载荷系统下人体膝关节生物力学特性进行研究,并进行有效性验证。建立膝关节有限元模型包括:股骨、胫骨、髌骨、腓骨、股骨软骨、胫骨软骨、腓骨软骨、半月板、前后交叉韧带、内外侧副韧带、髌韧带和股四头肌腱等。对膝关节施加1 kN轴向压缩载荷、134 N后向抽屉力和5、10、15 N[?m内翻力矩和外翻力矩,分析膝关节内软骨和半月板的接触应力和接触面积,股骨内外翻倾角以及位移变化情况。在1 kN压缩载荷和134 N抽屉力作用下,股骨软骨、内外侧半月板和内外侧胫骨软骨的接触应力峰值分别为4.47、3.25、2.83、2.70、2.53 MPa,Von Mises应力峰值分别为2.22、2.44、2.25、2.07、1.64 MPa。股骨相对胫骨前向位移为4.19 mm。施加5、10、15 N[?m内翻和外翻力矩时,股骨内翻和外翻倾角分别为3.49°、4.48°、4.91°和3.22°、3.62°、4.01°。随着力矩的线性增大,膝关节各组成部分的应力呈非线性变化趋势。膝关节软骨、半月板和韧带的研究结果符合其生物力学特性,与前人数值分析和实验研究结果相一致,可为临床膝关节生理病理分析和治疗提供一定的理论依据。     

The importance of femoral intramedullary entry point in knee arthroplasty

The purpose of this cadaveric study was to investigate how alignment of the femoral component in knee arthroplasty may be influenced by the entry site of the femoral intramedullary alignment rod. The angle between the rod and the distal femoral articular surface was measured in 20 non-arthritic cadaveric femurs using three different entry points. Entry points 10 mm anterior to the intercondylar notch and 8 mm medial to this point gave mean valgus angles of 8° (S.D. 1.0) and 10.2° (S.D. 1.0), respectively. Regression analysis showed no relationship between sex of the patient, body habitus, or leg length and valgus angulation of the distal femur. For total knee replacement in which the tibia is cut perpendicular to its axis in the coronal plane, thus eliminating 3° of tibial varus, we recommend using a femoral valgus angle of 5° with a hole anterior to the intercondylar notch and 7° with an anteromedial hole. Resecting the distal femur as recommended should enhance accuracy of component placement and survival of knee arthroplasties.     

In vivo kinematic analysis of posterior-stabilized total knee arthroplasty for the valgus knee operated by the gap-balancing technique

BackgroundMost in vivo kinematic studies of total knee arthroplasty (TKA) report on the varus knee. The objective of the present study was to evaluate in vivo kinematics of a posterior-stabilized fixed-bearing TKA operated on a valgus knee during knee bending in weight-bearing (WB) and non-weight-bearing (NWB).MethodsA total of sixteen valgus knees in 12 cases that underwent TKA with Scorpio NRG PS knee prosthesis and that were operated on using the gap balancing technique were evaluated. We evaluated the in vivo kinematics of the knee using fluoroscopy and femorotibial translation relative to the tibial tray using a 2-dimensional to 3-dimensional registration technique.ResultsThe average flexion angle was 111.3° ± 7.5° in WB and 114.9° ± 8.4° in NWB. The femoral component demonstrated a mean external rotation of 5.9° ± 5.8° in WB and 7.4° ± 5.2° in NWB. In WB and NWB, the femoral component showed a medial pivot pattern from 0° to midflexion and a bicondylar rollback pattern from midflexion to full flexion. The medial condyle moved similarly in the WB condition and in the NWB condition. The lateral condyle moved posteriorly at a slightly earlier angle during the WB condition than during the NWB condition.ConclusionsWe conclude that similar kinematics after TKA can be obtained with the gap balancing technique for the preoperative valgus deformity when compared to the kinematics of a normal knee, even though the magnitude of external rotation was small. Level of evidence: IV.     

Unicompartmental knee arthroplasties implanted for osteoarthritis with partial loss of joint space have high re-operation rates

The indications and contraindications for unicompartmental knee arthroplasty (UKA) are controversial. The aim of the study was to determine the risk factors for re-operation in our practice. A series of 113 medial UKAs with mean follow-up of 63 months were reviewed retrospectively. Pre-operatively all knees had radiographic or arthroscopic evidence of severe cartilage damage. The re-operation rate was not related to age, gender, arthroscopic finding or body mass index. It was related to the joint space on pre-operative standing weight bearing radiographs taken in extension. The re-operation rate was 6 (95% CI 2.1–17, P < 0.001) times higher when the thickness of the pre-operative medial joint space was > 2 mm rather than ≤ 2 mm. It was 8 (95% CI 2.8–22.5, P < 0.001) times higher when the thickness of the pre-operative medial space was > 40% of the thickness of the lateral space. The ratio of pre-operative joint spaces has a greater influence on revision rate than the absolute measurement and is independent of radiographic magnification or the patient's normal cartilage thickness. We therefore recommend that, in medial knee osteoarthritis, UKA should only be used if the pre-operative medial joint space on standing radiographs is ≤ 40% of the lateral joint space, even if severe cartilage damage is seen arthroscopically.     

A preliminary modeling investigation into the safe correction zone for high tibial osteotomy

Background

High tibial osteotomy (HTO) re-aligns the weight-bearing axis (WBA) of the lower limb. The surgery reduces medial load (reducing pain and slowing progression of cartilage damage) while avoiding overloading the lateral compartment. The optimal correction has not been established. This study investigated how different WBA re-alignments affected load distribution in the knee, to consider the optimal post-surgery re-alignment.

Effect of femoral component position on biomechanical outcomes of unicompartmental knee arthroplasty

Background

The positions of unicompartmental femoral components do not always follow the neutral center of the medial distal femoral condyle. The biomechanical effect of the center of the distal femoral condyle has not yet been evaluated, and the optimal femoral position in unicompartmental knee arthroplasty (UKA) is yet to be biomechanically justified. The purpose of this study was to evaluate, using finite element analysis, the effect of the center of the distal femoral component on the biomechanical outcomes of UKA with respect to the contact stresses in the polyethylene (PE) insert and articular cartilage.

前交叉韧带重建术后关节粘连患者在体胫股关节运动学分析

目的 定量分析前交叉韧带重建(anterior cruciate ligament reconstruction, ACLR)术后关节粘连患者在体胫股关节 6 自由度的运动学特征。 方法 纳入 15 例 ACLR 术后关节粘连患者和 15 例健康受试者,运用便携式膝关节三维运动分析系统采集受试者负重屈膝和非负重屈膝时胫股相对于股骨的运动轨迹,获取胫股关节 6 自由度的运动学数据。 结果 与健康人相比,负重屈膝 30°、45°、60°和 75°时,膝关节粘连患者患侧胫骨内旋角度明显减少(P<0. 001);负重屈膝 30° 和 45° 时,膝关节粘连患者患侧胫骨相对于股骨的外翻角度较健康人明显减小(P<0. 05)。 非负重屈膝 75°时,膝关节粘连患者患侧胫骨内移距离较健康人明显减少(P<0. 05)。 结论 关节粘连限制了胫骨相对于股骨的旋转和内外移,对于胫骨相对于股骨的前后移动影响不大。 因此,临床上应该利用各种治疗手段松解股骨内外侧沟的粘连和外侧副韧带挛缩,解决旋转和内外移动受限的问题,以最大程度恢复膝关节功能。     

Knee kinematics after cruciate retaining highly congruent mobile bearing total knee arthroplasty: An in vivo dynamic RSA study

PurposeThis work presents a kinematic evaluation of a cruciate retaining highly congruent mobile bearing total knee arthroplasty design using dynamic Roentgen sterephotogrammetric analysis. The aim was to understand the effect of this implant design on the kinematics of prosthetic knees during dynamic activities.MethodsA cohort of 15 patients was evaluated at nine month follow-up after surgery. The mean age was 74.8 (range 66–85) years.The kinematics was evaluated using the Grood and Suntay decomposition and the Low-Point (LP) methods.Results?tlsb=-0.15pt?>From sitting to standing up position, the femoral component internally rotated (from − 11.3 ± 0.2° to − 7.0 ± 0.2°). Varus–valgus rotations were very close to 0° during the whole motor task.LP of medial condyle moved from an anterior position of 12.0 ± 0.2 mm to a posterior position of − 12.4 ± 0.2 mm; LP of the lateral condyle moved from an anterior position of 8.1 ± 0.2 mm to a posterior position of − 12.4 ± 0.2 mm, showing a bi-condylar rollback where both condyles moved parallel backward. Moreover, the femoral component showed anterior translation with respect to the tibia from 80° to 20° (from − 4.9 ± 0.2 mm to 3.3 ± 0.2 mm), then a posterior translation from 20° to full extension was identified (from 3.3 ± 0.2 mm to 0.5 ± 0.2 mm).ConclusionsParadoxical anterior femoral translation and absence of medial-pivoting motion were recorded, highlighting the role of the symmetric deep dishes insert as main driver of the kinematic of this TKA design.     

Mobile vs. fixed bearing unicondylar knee arthroplasty: A randomized study on short term clinical outcomes and knee kinematics

The literature contains limited yet controversial information regarding whether a fixed or a mobile bearing implant should be used in unicompartmental knee arthroplasty (UKA). This randomized study was to further document the performance and comparison of the two designs. Fifty-six knees in 48 patients (mean age of 72 years) undergoing medial UKA were randomized into a fixed bearing (Miller/Galante) or a mobile bearing (Oxford) UKA. The 2 year clinical outcomes (clinical scores), radiographic findings, and weight bearing knee kinematics (assessed using RSA) were compared between the two groups. The mobile bearing knees displayed a larger and an incrementally increased tibial internal rotation (4.3 degrees, 7.6 degrees, 9.5 degrees vs. 3.0 degrees, 3.0 degrees, 4.2 degrees respectively at 30 degrees, 60 degrees, 90 degrees of knee flexion) compared to the fixed ones. The medial femoral condyle in the mobile bearing knees remained 2 mm from the initial position vs. a 4.2 mm anterior translation in the fixed bearing knees during knee flexion. The contact point in the mobile bearing implant moved 2 mm posteriorly vs. a 6 mm anterior movement in the other group. The mobile bearing knees had a lower incidence of radiolucency at the bone implant interface (8% vs. 37%, p < 0.05). The incidence of lateral compartment OA and progression of OA at patello-femoral joint were equal. No differences were found regarding Knee Society Scores, WOMAC, and SF-36 scores (p > 0.05). This study indicates that mobile bearing knees had a better kinematics, a lower incidence of radiolucency but not yet a better knee function at 2 years.